Co-reporter:Changlei Wang, Lei Guan, Dewei Zhao, Yue Yu, Corey R. Grice, Zhaoning Song, Rasha A. Awni, Jing Chen, Jianbo Wang, Xingzhong Zhao, and Yanfa Yan
ACS Energy Letters September 8, 2017 Volume 2(Issue 9) pp:2118-2118
Publication Date(Web):August 21, 2017
DOI:10.1021/acsenergylett.7b00644
Tin oxide (SnO2) electron selective layers (ESLs) processed by low-temperature plasma-enhanced atomic layer deposition (PEALD) hold promise for fabricating lightweight and efficient flexible lead halide perovskite solar cells (PVSCs). However, the as-synthesized SnO2 ESLs typically lead to flexible PVSCs with lower open-circuit voltage (VOC) and fill factor (FF) as well as a higher degree of current density–voltage (J–V) hysteresis, compared to PVSCs fabricated on rigid substrates. Here, we report that facile water vapor treatment of PEALD-synthesized SnO2 ESLs can effectively improve the VOC and FF while reducing the degree of J–V hysteresis. The improvement in device performance is mainly attributed to the improved conductivity and electrical mobility of SnO2 ESLs enabled by water vapor treatment. With such treatment, our best flexible PVSC fabricated on a commercial substrate shows a power conversion efficiency of 18.36 (17.12)% when measured under a reverse (forward) voltage scan and a stabilized efficiency of 17.08%, which is the highest reported efficiency for flexible PVSCs with the regular structure.
Co-reporter:Changlei Wang;Chuanxiao Xiao;Yue Yu;Dewei Zhao;Rasha A. Awni;Corey R. Grice;Kiran Ghimire;Iordania Constantinou;Weiqiang Liao;Alexer J. Cimaroli;Pei Liu;Jing Chen;Nikolas J. Podraza;Chun-Sheng Jiang;Mowafak M. Al-Jassim;Xingzhong Zhao;Yanfa Yan
Advanced Energy Materials 2017 Volume 7(Issue 17) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/aenm.201700414
Through detailed device characterization using cross-sectional Kelvin probe force microscopy (KPFM) and trap density of states measurements, we identify that the J–V hysteresis seen in planar organic–inorganic hybrid perovskite solar cells (PVSCs) using SnO2 electron selective layers (ESLs) synthesized by low-temperature plasma-enhanced atomic-layer deposition (PEALD) method is mainly caused by the imbalanced charge transportation between the ESL/perovskite and the hole selective layer/perovskite interfaces. We find that this charge transportation imbalance is originated from the poor electrical conductivity of the low-temperature PEALD SnO2 ESL. We further discover that a facile low-temperature thermal annealing of SnO2 ESLs can effectively improve the electrical mobility of low-temperature PEALD SnO2 ESLs and consequently significantly reduce or even eliminate the J–V hysteresis. With the reduction of J–V hysteresis and optimization of deposition process, planar PVSCs with stabilized output powers up to 20.3% are achieved. The results of this study provide insights for further enhancing the efficiency of planar PVSCs.
Co-reporter:Changlei Wang, Dewei Zhao, Yue Yu, Niraj Shrestha, Corey R. Grice, Weiqiang Liao, Alexander J. Cimaroli, Jing Chen, Randy J. Ellingson, Xingzhong Zhao, Yanfa Yan
Nano Energy 2017 Volume 35(Volume 35) pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.nanoen.2017.03.048
•Compositional and morphological engineering leads to 20% efficiency perovskite solar cells.•The best-performing flexible perovskite solar cell achieved an efficiency of 17.96%.•Mixing formamidinium and methylammonium extends the absorption range to longer wavelength ranges.•Pb(SCN)2 additive significantly improves the quality of perovskite films.We report on compositional and morphological engineering of mixed methylammonium (MA) and formamidinium (FA) lead triiodide (MA1−xFAxPbI3) perovskite absorber layers to produce highly efficient planar and flexible perovskite solar cells (PVSCs) with reduced hysteresis. Incorporation of FA into the MAPbI3 extends the absorption edge of the perovskite to longer wavelengths, leading to enhanced photocurrent of the resultant PVSCs. Moreover, adding a small amount of lead thiocyanate (Pb(SCN)2) additive into mixed perovskite precursor solutions significantly enlarges the grain size and prolongs the carrier lifetime, leading to improved device performance. With optimal compositional and morphological engineering, the average power conversion efficiency (PCE) improves from 15.74±0.74% for pure MAPbI3 PVSCs to 19.40±0.32% for MA0.7FA0.3PbI3 PVSCs with 3% Pb(SCN)2 additive, exhibiting a high reproducibility and small hysteretic behavior. The best PVSC achieves a PCE of 20.10 (19.85)% measured under reverse (forward) voltage scan. Furthermore, the compositional and morphological engineering allowed the fabrication of efficient flexible PVSCs on indium-doped SnO2 (ITO)/polyethylene terephthalate (PET) substrates, with the best PCE of 17.96 (16.10)% with a VOC of 1.076 (1.020) V, a JSC of 22.23 (22.23) mA/cm2 and a FF of 75.10 (71.02)% when measured under reverse (forward) voltage scan. Our approach provides an effective pathway to fabricate highly efficient and reproducible planar PVSCs.Mixing MAPbI3 precursor with FAPbI3 precursor with the presence of Pb(SCN)2 additive significantly improves crystal quality of mixed cation lead halide perovskite thin films and, therefore, the performances of the resulting perovskite solar cells. The low temperature (100 °C) fabrication process enables us to achieve flexible perovskite solar cells efficiencies up to 17.96%.Download high-res image (314KB)Download full-size image
Co-reporter:Zhaobo He;Feng Guo;Chun Feng;Bo Cai;James P. Lata;Rongxiang He;Qinqin Huang;Xiaolei Yu;Lang Rao;Huiqin Liu;Shishang Guo;Wei Liu;Yuanzhen Zhang;Tony Jun Huang;Xingzhong Zhao
Journal of Materials Chemistry B 2017 vol. 5(Issue 2) pp:226-235
Publication Date(Web):2017/01/04
DOI:10.1039/C6TB02558G
Cell-free DNA has been widely used in non-invasive prenatal diagnostics (NIPD) nowadays. Compared to these incomplete and multi-source DNA fragments, fetal nucleated red blood cells (fNRBCs), once as an aided biomarker to monitor potential fetal pathological conditions, have re-attracted research interest in NIPD because of their definite fetal source and the total genetic information contained in the nuclei. Isolating these fetal cells from maternal peripheral blood and subsequent cell-based bio-analysis make maximal genetic diagnosis possible, while causing minimal harm to the fetus or its mother. In this paper, an affinity microchip is reported which uses hydroxyapatite/chitosan nanoparticles as well as immuno-agent anti-CD147 to effectively isolate fNRBCs from maternal peripheral blood, and on-chip biomedical analysis was demonstrated as a proof of concept for NIPD based on fNRBCs. Tens of fNRBCs can be isolated from 1 mL of peripheral blood (almost 25 mL−1 in average) from normal pregnant women (from the 10th to 30th gestational week). The diagnostic application of fNRBCs for fetal chromosome disorders (Trisomy 13 and 21) was also demonstrated. Our method offers effective isolation and accurate analysis of fNRBCs to implement comprehensive NIPD and to enhance insights into fetal cell development.
Co-reporter:Hadja Fatima Mehnane;Changlei Wang;Kiran Kumar Kondamareddy;Wenjing Yu;Weiwei Sun;Haimin Liu;Sihang Bai;Wei Liu;Shishang Guo
RSC Advances (2011-Present) 2017 vol. 7(Issue 4) pp:2358-2364
Publication Date(Web):2017/01/04
DOI:10.1039/C6RA26012H
Strontium (Sr) doped TiO2 nanoparticles are investigated with a view to studying the performance parameters of dye sensitized solar cells (DSSCs). Sr is used in trace levels (parts per million, ppm hereafter). The Sr doped TiO2 and undoped TiO2 nanoparticles are synthesized by the hydrothermal method and thin films of TiO2 electrodes are prepared using these particles (average grain size of 24 nm). The electrodes are characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), surface area (BET) and UV-vis absorption spectrometry. DSSCs are fabricated using the doped and undoped TiO2 nanoparticle photoanodes. Their photovoltaic characteristics are studied by employing J–V measurements and electrochemical impedance spectroscopy (EIS). XRD studies reveal that the doping of Sr into the TiO2 lattice slightly inhibits the growth of the particles and causes lattice distortions. The optical studies indicate a reduction in band-gap upon doping of TiO2 films and a simultaneous enhancement in the photocurrent density (Jsc) and the photovoltage (Voc). The photoanode doped with 50 ppm Sr exhibits the highest power conversion efficiency (PCE) of about 7.88% which is 12.73% higher than that of undoped TiO2 cells. The effect of the Sr dopant on electron transport is studied by using EIS measurements. An improvement in electron life time is observed on the doping of TiO2.
Co-reporter:Zhenhua Yu;Bolei Chen;Pei Liu;Changlei Wang;Chenhao Bu;Nian Cheng;Sihang Bai;Yanfa Yan;Xingzhong Zhao
Advanced Functional Materials 2016 Volume 26( Issue 27) pp:4866-4873
Publication Date(Web):
DOI:10.1002/adfm.201504564
Within the past few years, the record efficiency of inorganic–organic perovskite solar cell (PSC) has improved rapidly up to over 20%. However, the viability of commercialization of the PSC technology has been seriously questioned due to the moisture- and thermal-induced instabilities. Here, it is demonstrated that these issues may be mitigated via cell structure design and contact engineering. By employing the hole-conductor layer-free cell structure and a bi-layer back contact consisting of a carbon/CH3NH3I composite layer and a compact hydrophobic carbon layer, the PSCs have shown excellent stability, inhibiting moisture ingression and heat-induced perovskite degradation. It is found that, the unique bi-layer contact enables the optimization of perovskite absorbers during thermal stress. As a result, instead of degradation, the devices present enhanced performance under heating at 100 °C for 30 min. The best-performing cell shows a final efficiency of 13.6% from an initial efficiency of 11.3% after thermal stress. Upon encapsulation, these cells can even retain 90% of the initial efficiencies after water exposure and over 100% initial efficiency under thermal stress at 150 °C for half an hour. This approach provides a facile way for stabilizing the PSCs and opens a door for viable commercialization of the emerging PSC technology.
Co-reporter:Zhenhua Yu, Fei Qi, Pei Liu, Sujian You, Kiran Kumar Kondamareddy, Changlei Wang, Nian Cheng, Sihang Bai, Wei Liu, Shishang Guo and Xing-zhong Zhao
Nanoscale 2016 vol. 8(Issue 11) pp:5847-5851
Publication Date(Web):22 Feb 2016
DOI:10.1039/C5NR09045H
A novel composite nanostructured titanium dioxide (TiO2) based electron-transport layer (ETL) is designed by combining size blended nanoparticles (SBNP) and nanoarrays (NA) for efficient perovskite solar cell (PSC) applications. The composite nanostructured (SBNP + NA) ETL is successfully employed in hole-conductor free PSCs, there by achieving a stable device with a maximum efficiency of 13.5%. The improvement in the performance is attributed to the better charge transport and lower recombination in the SBNP + NA ETL. Despite the stable high efficiency, SBNP + NA ETL based PSCs are advantageous owing to their low cost, ease of all-solution fabrication process in an open environment and good reproducibility.
Co-reporter:Changlei Wang, Dewei Zhao, Corey R. Grice, Weiqiang Liao, Yue Yu, Alexander Cimaroli, Niraj Shrestha, Paul J. Roland, Jing Chen, Zhenhua Yu, Pei Liu, Nian Cheng, Randy J. Ellingson, Xingzhong Zhao and Yanfa Yan
Journal of Materials Chemistry A 2016 vol. 4(Issue 31) pp:12080-12087
Publication Date(Web):11 Jul 2016
DOI:10.1039/C6TA04503K
Recent progress has shown that low-temperature processed tin oxide (SnO2) is an excellent electron selective layer (ESL) material for fabricating highly efficient organic–inorganic metal-halide perovskite solar cells with a planar cell structure. Low-temperature processing and a planar cell structure are desirable characteristics for large-scale device manufacturing due to their associated low costs and processing simplicity. Here, we report that plasma-enhanced atomic layer deposition (PEALD) is able to lower the deposition temperature of SnO2 ESLs to below 100 °C and still achieve high device performance. With C60-self-assembled monolayer passivation, our PEALD SnO2 ESLs deposited at ∼100 °C led to average power conversion efficiencies higher than 18% (maximum of 19.03%) and 15% (maximum of 16.80%) under reverse voltage scan for solar cells fabricated on glass and flexible polymer substrates, respectively. Our results thus demonstrate the potential of the low-temperature PEALD process of SnO2 ESLs for large-scale manufacturing of efficient perovskite solar cells.
Co-reporter:Shaofu Wang, Dandan Qu, Yun Jiang, Wan-Sheng Xiong, Hong-Qian Sang, Rong-Xiang He, Qidong Tai, Bolei Chen, Yumin Liu, and Xing-Zhong Zhao
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 31) pp:20040
Publication Date(Web):July 15, 2016
DOI:10.1021/acsami.6b05559
Three-dimensional branched TiO2 architectures (3D BTA) with controllable morphologies were synthesized via a facile template-free one-pot solvothermal route. The volume ratio of deionized water (DI water) and diethylene glycol in solvothermal process is key to the formation of 3D BTA assembled by nanowire-coated TiO2 dendrites, which combines the advantages of 3D hierarchical structure and 1D nanoscale building blocks. Benefiting from such unique structural features, the BTA in full bloom achieved significantly increased specific surface areas and shortened Li+ ion/electrons diffusion pathway. The lithium-ion batteries based on BTA in full bloom exhibited remarkably enhanced reversible specific capacity and rate performance, attributing to the high contact area with the electrolyte and the short solid state diffusion pathway for Li+ ion/electrons promoting lithium insertion and extraction.Keywords: controllable morphology; hierarchical architecture; lithium-ion battery; nanowire-coated dendrite; TiO2 anode
Co-reporter:Qinqin Huang;Bo Cai;Bolei Chen;Lang Rao;Zhaobo He;Rongxiang He;Feng Guo;Libo Zhao;Kiran Kumar Kondamareddy;Wei Liu;Shishang Guo
Advanced Healthcare Materials 2016 Volume 5( Issue 13) pp:1554-1559
Publication Date(Web):
DOI:10.1002/adhm.201500981
Co-reporter:Nian Cheng, Pei Liu, Sihang Bai, Zhenhua Yu, Wei Liu, Shi-Shang Guo, Xing-Zhong Zhao
Journal of Power Sources 2016 Volume 319() pp:111-115
Publication Date(Web):1 July 2016
DOI:10.1016/j.jpowsour.2016.04.062
•A simple solvent treatment process is introduced.•Morphology of PbI2 film is modified by the solvent treatment.•More complete conversion of PbI2 to CH3NH3PbI3 is observed.•Enhanced performance and reproducibility is obtained.The morphology of PbI2 film plays a critical role in determining the quality of the resultant CH3NH3PbI3 film and power conversion efficiency of CH3NH3PbI3 perovskite solar cell. Here, we propose a solvent treatment method in the two-step sequential deposition process to control the morphology of PbI2 film, which leads to enhanced power conversion efficiency. Hole transport material free perovskite solar cell is chosen as a paradigm to demonstrate this idea. Solvent (isopropanol, chlorobenzene, or ethanol) treated PbI2 films exhibit dendrite-like or flake-like morphologies, which facilitate more complete conversion of PbI2 to CH3NH3PbI3 perovskite in ambient atmosphere with a relative high humidity. Therefore, enhanced performance is obtained with the solvent treated PbI2 films. Average power conversion efficiency has been improved from 9.42% in the traditional two-step sequential deposition to 11.22% in solar cells derived from ethanol treated PbI2 films.
Co-reporter:Nian Cheng, Pei Liu, Sihang Bai, Zhenhua Yu, Wei Liu, Shi-Shang Guo, Xing-Zhong Zhao
Journal of Power Sources 2016 Volume 321() pp:71-75
Publication Date(Web):30 July 2016
DOI:10.1016/j.jpowsour.2016.04.124
•Mesoporous SiO2 is prepared by spin-coating.•SiO2 layer can act as an efficient insulating layer.•Higher power conversion efficiency is obtained with TiO2/SiO2 films.A mesoporous SiO2 layer is successfully introduced into the hole transport material free perovskite solar cells by spin-coating a SiO2 paste onto the TiO2 scaffold layer. This SiO2 layer can act as an insulating layer and effectively inhibit the charge recombination between the TiO2 layer and carbon electrode. The variation of power conversion efficiencies with the thickness of SiO2 layer is studied here. Under optimized SiO2 thickness, perovskite solar cell fabricated on the TiO2/SiO2 film shows a superior power conversion efficiency of ∼12% and exhibits excellent long time stability for 30 days.
Co-reporter:Pei Liu, Zhenhua Yu, Nian Cheng, Changlei Wang, Youning Gong, Sihang Bai, Xing-Zhong Zhao
Electrochimica Acta 2016 Volume 213() pp:83-88
Publication Date(Web):20 September 2016
DOI:10.1016/j.electacta.2016.07.095
•A facile approach to fabricate low-cost perovskite solar cell is introduced.•Controllable morphology and properties of TiO2 electron-transport layer.•Commercial P25 nanoparticles and bilayer hybrid carbon electrode is applied.•Enhanced performance is observed.•Excellent long-term stability together with reduced hysteresis is obtained.A facile approach to fabricate low-cost hole-transport-material (HTM)-free perovskite solar cell(PSC) based on commercial P25 nanoparticles and bilayer hybrid carbon electrode under ambient condition is reported. The performance of such HTM-free PSCs are highly dependent on the thickness and morphology of the P25 based TiO2 electron-transport layer(ETL), which can be adjusted by the amount of ethanol and ethyl cellulose in the paste. After optimization, a power conversion efficiency of 12.48% is obtained, which is enhanced by 20.46% compared with solar cells employing hydrothermal TiO2 ETL. In addition, PSCs with P25 ETL also exhibit excellent long-term stability together with reduced hysteresis. With advantages of low-cost, high efficiency and facile fabrication process, commercial P25 nanoparticles based PSC is highly potential for future commercialization.
Co-reporter:Ping-Li Qin;Hong-Wei Lei;Xiao-Lu Zheng;Qin Liu;Hong Tao;Guang Yang;Wei-Jun Ke;Liang-Bin Xiong;Ming-Chao Qin;Guo-Jia Fang
Advanced Materials Interfaces 2016 Volume 3( Issue 14) pp:
Publication Date(Web):
DOI:10.1002/admi.201500799
To achieve high performance for inverted structure perovskite solar cells, the design of hole-transporting layer (HTL) and related interfacial engineering are very important tasks. To avoid the hygroscopic characteristics of poly (3, 4-ethylenedioxythiophene):poly (styrenesulfonate) that may degrade the adjacent moisture-sensitive perovskite layer, here, a new CrOx-based hole-transport material has been introduced. The feasibility of fabrication efficient perovskite solar cells with CrOx and Cu-CrOx as HTLs is confirmed for the first time. Cu doping can modify the chromium ion contents and suppress the formation of surface hydroxylation and CrO3 in the CrOx film, which can increase work function, electrical conductivity, and carrier mobility of the CrOx films. Consequently, the power conversion efficiency of the corresponding device increases to 10.99% from its original value of 9.27%. This study not only provides a novel HTL system for high performance and decently stable optoelectronic devices but also reveals the importance of HTL doping for interface engineering.
Co-reporter:Yumin Liu, Li Yu, Yun Jiang, Wansheng Xiong, Qian Wang, Jian Sun, Huai Yang, Xing-Zhong Zhao
Nano Energy 2016 Volume 26() pp:648-656
Publication Date(Web):August 2016
DOI:10.1016/j.nanoen.2016.06.021
•Self-organized cholesteric liquid crystal polymer films were prepared via a facile photopolymerization process.•CLC polymer films with selective light reflections were applied as transparent and flexible back-reflectors for DSCs.•The optical thickness of DSC can be remarkably increased while retaining the cell transparency.•The enhancement of DSC performances reveals strong wavelength dependence owing to the tunable photonic band gap of CLCs.Dye-sensitized solar cells (DSCs) have attracted widespread attention in recent years, attributed to their low production costs, facile fabrication and tunable optical properties. In order to achieve competitive conversion efficiencies, the sunlight harvesting capacities of DSCs should be improved over a broad range of wavelengths and incidence angle. Here, we demonstrate a facile strategy to enhance the light absorptions of the devices via employing self-organized cholesteric liquid crystal (CLC) polymer films as transparent and flexible back-reflectors for DSCs. The photonic band gap of these CLC films can be precisely tailored by modulating the helical pitch and twist sense. The selective light reflection of these CLC films gives rise to the possibility for increasing the optical path length of the light in particular wavelength region while retaining the cell transparency. The enhancement of photocurrent and power conversion efficiency (PCE) reveals strong wavelength dependence owing to the selective reflection of these CLC polymer films. The DSCs with proper combination of CLC back-reflectors yield the maximum enhancement over 21% in photocurrent and 17% in PCE. The work presented here provides new insights into the design of cell geometry for achieving extra absorption enhancement, which can also be compatible with other photovoltaic concepts.Self-organized cholesteric liquid crystal polymer films with selective light reflection are designed as transparent and flexible back-reflectors for dye-sensitized solar cells to improve the light-harvesting capacities in particular wavelength region, while maintaining a transparent appearance of the device. This strategy provides new guidance on the design of cell geometry with enhanced light absorptions and develops the application of cholesteric liquid crystal in photovoltaic devices.
Co-reporter:Bo Cai;Rongxiang He;Xiaolei Yu;Lang Rao;Zhaobo He
Microfluidics and Nanofluidics 2016 Volume 20( Issue 4) pp:
Publication Date(Web):2016 April
DOI:10.1007/s10404-016-1725-2
In this work, we developed a shape-controllable nozzle inside a multilayer PDMS microchip. The nozzle was able to control the shape of the fluid channel in three dimensions. All the four walls of the fluid channel were comprised of pneumatic PDMS membrane valves, and their deformation was controlled by air pressure. As both the limitation of the fluid flux and the shape of the fluid channel were adjustable spatially in three dimensions, this valve-based nozzle generated droplets with less response time and in a more effectively controlled manner comparing to conventional droplet devices. It could also function as a microinjector to modulate the compositions of droplets precisely and continuously. In addition, the nozzle was able to form a specific shape to generate core–shell particles.
Co-reporter:Weiwei Sun, Huiqin Liu, Tao Peng, Yumin Liu, Gongxun Bai, Sen Kong, Shishang Guo, Meiya Li and Xing-Zhong Zhao
Journal of Materials Chemistry A 2015 vol. 3(Issue 15) pp:8165-8170
Publication Date(Web):06 Mar 2015
DOI:10.1039/C5TA00752F
Porous micrometer-sized architecture that consists of aggregated single-crystalline nanoparticles is critical for LiMn2O4 to achieve good rate capacity and cycling stability, since it can increase the contact area between the electrolyte/electrode and shorten the transport paths for electrons and lithium ions. In this paper, hierarchical porous donut-shaped LiMn2O4 comprising aggregated single-crystalline nanoparticles has been successfully fabricated with MnO2 nanosheet coated polystyrene spheres as a precursor and characterized in terms of structure and performance as the cathode for lithium ion batteries. The charge/discharge tests show that the as-obtained donut-shaped LiMn2O4 exhibits excellent rate capability and high-rate cyclic stability. Surprisingly, even at a high charge/discharge rate of 10 C, the battery yields a capacity retention of over 95% after 500 cycles. The superior performance of the synthesized product can be attributed to its intrinsic structure: porous donut-shaped LiMn2O4 consisting of well-connected single-crystalline nanoparticles. The interpenetrating nanoparticle reduces the path of Li ion diffusion and increases the number of reaction sites for lithium insertion/extraction; the pores provide void space to buffer the volume changes during high-rate charge/discharge.
Co-reporter:Weiwei Sun, Huiqin Liu, Yumin Liu, Gongxun Bai, Wei Liu, Shishang Guo and Xing-Zhong Zhao
Nanoscale 2015 vol. 7(Issue 31) pp:13173-13180
Publication Date(Web):02 Jul 2015
DOI:10.1039/C5NR02057C
Control over one-dimensional growth of spinel-type LiMn2O4 nanowires is challenging in the area of materials science due to their cubic crystal structure. The current strategy is to use a self-support template to fabricate LiMn2O4 nanowires, which is time-consuming and limits their large-scale commercial production. In this paper, we propose a general strategy to construct well-defined LiMn2O4 nanowires terminated with amorphous carbon at the edges by an ingenious method without using any template. Benefited from its unique carbon-coated nanowire structure, the electrode exhibits a capacitor-like rate performance and battery-like high capacity for long-time cycling. Even after 1500 cycles at an extremely high current density of 30 C, approximately 82% of its initial capacity can still be retained. Significantly, the strategy reported here will be beneficial and revelatory to manufacture other extensive one-dimensional robust carbon-decorated nanowires, paving new ways for future developments of ultrafast rechargeable lithium-ion batteries.
Co-reporter:Changlei Wang, Zhenhua Yu, Chenghao Bu, Pei Liu, Sihang Bai, Chang Liu, Kiran Kumar Kondamareddy, Weiwei Sun, Kan Zhan, Kun Zhang, Shishang Guo, Xingzhong Zhao
Journal of Power Sources 2015 Volume 282() pp:596-601
Publication Date(Web):15 May 2015
DOI:10.1016/j.jpowsour.2015.02.092
•Al2O3 and TiO2 are combined together to form Al2O3/TiO2 hybrid blocking for the first time.•Al2O3/TiO2 hybrid blocking layer is synthesized by a simple and low-cost spin coating method.•Al2O3 overlayer can retard interfacial recombination, while TiO2 tiny particles facilitate electrons diffusion.•The conversion efficiency has a significant improvement of 29%.A facile way of fabricating efficient blocking layer on mesoporous TiO2 film of dye-sensitized solar cells (DSSCs) is demonstrated here for the first time. Al2O3 and TiO2 are combined together to form a blocking layer. A simple spin coating technique is employed which is a versatile and low-cost method over the atomic layer deposition (ALD) technique. Multifunctional alumina/titania (Al2O3/TiO2) hybrid overlayer is prepared on traditional TiO2 nanocrystalline thin film surface, through sequential deposition of AlCl3·6H2O and TiCl4 precursor solutions followed by sintering at 500 °C for 30 min. Al2O3 effectively plays its role in retarding interfacial recombination of electrons and improving open circuit potential (Voc), while the tiny TiO2 clusters synthesized from TiCl4 treatment act as electron transporting channels to facilitate electron diffusion which leads to enhanced photocurrent (Jsc). Compared to the device without blocking layer, the DSSCs assembled with Al2O3/TiO2 hybrid blocking layer showed improvement in Jsc (from 13.09 mA/cm2 to 16.90 mA/cm2) as well as in Voc (from 0.72 V to 0.73 V) resulting a much better conversion efficiency of 8.60%.
Co-reporter:Liu Yumin, Zhang Minli, Jiang Yun, Xia Yu, Sun Weiwei, Zhao Xing-Zhong
Electrochimica Acta 2015 Volume 173() pp:483-489
Publication Date(Web):10 August 2015
DOI:10.1016/j.electacta.2015.05.102
We demonstrate a general strategy to construct hierarchical TiO2 nanorod arrays (HTNRs) coupling with plasmon resonant metallic nanoparticles for dye-sensitized solar cells (DSCs). The electron transfer and interfacial recombination process have been optimized via the construction of photoanodes. Moreover, localized electric fields produced by the introduction of Au nanoparticles could excite dye molecules more effectively than the incident far-field light, resulting in further enhancement of light adsorption and photocurrent generation of DSCs. The synergistic effect of surface plasmon resonance (SPR) and constructed HTNRs has been investigated by optical spectroscopy, J-V, IPCE, EIS and OCVD measurements. An evidently improvement in energy conversion efficiency of the devices beyond 25% has been achieved via the cooperation of constructed HTNRs and SPR effects in DSCs.The general strategy reported here will offer a facile approach to improve the electron transfer process via the construction of HTNRs, and to further enhance the light harvesting of dye molecules by introduction of SPR effects.
Co-reporter:Qidong Tai and Xing-Zhong Zhao
Journal of Materials Chemistry A 2014 vol. 2(Issue 33) pp:13207-13218
Publication Date(Web):16 Jun 2014
DOI:10.1039/C4TA01404A
Bifacial dye-sensitized solar cells (DSCs) that are able to utilize the incidental light from both their front- and rear-side have received increasing attention in recent years. Compared to conventional DSCs that can only be operated under front-side illumination, bifacial design will allow DSCs to generate up to 50% more electrical power. Besides, bifacial DSCs can be easily made transparent and may find broad applications in building integrated photovoltaics (BIPV) as power-generating windows and roof panels. Transparent counter electrodes (CEs) are key to the fabrication of bifacial DSCs. However, despite the fact that conventional Pt CE can be made transparent, its high cost and scarce source may hinder the large-scale application of DSCs. Therefore, many efforts have been made to develop low-cost alternative CEs based on carbon materials, conducting polymers, inorganic compounds and their composites. In this feature article, we intend to pay special attention to the recent advances in the development of Pt-free transparent CEs and highlight their applications in bifacial DSCs.
Co-reporter:Zhenhua Yu, Sujian You, Changlei Wang, Chenghao Bu, Sihang Bai, Ziyao Zhou, Qidong Tai, Wei Liu, Shishang Guo and Xing-zhong Zhao
Journal of Materials Chemistry A 2014 vol. 2(Issue 24) pp:9007-9010
Publication Date(Web):18 Mar 2014
DOI:10.1039/C4TA00837E
A highly environmentally-friendly ubiquinone 10 (UQ10) based I2-free electrolyte, which is inspired by photosynthesis, is employed in dye-sensitized solar cells (DSSCs) under 100 mW cm−2 (AM 1.5G) illumination. Profiting from this UQ10 based electrolyte a 10% increased power conversion efficiency of 8.18% is achieved compared with the traditional one containing I2 (7.44%). The superior performance of this UQ10 based electrolyte is mainly derived from the lower visible light wastage and high catalytic activity to the counter electrode as revealed by photoelectrochemical characterization. Moreover, being widely adopted in cardiovascular medicine and cosmetics, UQ10 is a very safe and low-cost choice for DSSCs. With the advantages of high power conversion efficiency, bio-safety, universal dye compatibility and diversity of molecular design, UQ10 is very promising to be widely applied in DSSCs, and perovskite based solar cells.
Co-reporter:Pingli Qin, Guojia Fang, Weijun Ke, Fei Cheng, Qiao Zheng, Jiawei Wan, Hongwei Lei and Xingzhong Zhao
Journal of Materials Chemistry A 2014 vol. 2(Issue 8) pp:2742-2756
Publication Date(Web):25 Nov 2013
DOI:10.1039/C3TA13579A
Efficient organic solar cells (OSCs) based on regioregular poly(3-hexylthiophene):fullerene derivative [6,6]-phenyl-C61butyric acid methyl ester composites have been fabricated on fluorine-doped tin oxide (FTO) coated glass substrates by a radio frequency (RF) sputtered and ultraviolet ozone (UVO) treated MoS2 film as the hole-transport layer (HTL). With the help of X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, Raman spectroscopy, transmission spectra and the Hall-effect system, we find that the deposition temperature can modulate the contents of the various valence states of molybdenum, which can result in changes of the energy level, and the optical and electrical properties of the MoS2 films. MoS2 has been oxidized to a double-layered MoO3–MoS2 film by UVO treatment. Due to the presence of the molybdenum oxidation states Mo5+ and Mo6+, the MoS2 film shows p-type conductive behavior, and its smaller electron affinity can effectively block electron from exciton dissociation. By optimizing the HTL thickness and sputtering deposition temperature, a power conversion efficiency up to 4.15% has been achieved for an OSC that used a double-layered MoO3–MoS2 film as the HTL. Its JSC is bigger than that of the OSC with a pure MoO3 film as the HTL. This shows that this double layer MoO3–MoS2 interface is more favorable for hole-transfer.
Co-reporter:Ziyao Zhou, Jiahong Wang, Fan Nan, Chenghao Bu, Zhenhua Yu, Wei Liu, Shishang Guo, Hao Hu and Xing-Zhong Zhao
Nanoscale 2014 vol. 6(Issue 4) pp:2052-2055
Publication Date(Web):20 Nov 2013
DOI:10.1039/C3NR04315K
Upconversion materials have been employed as energy relay materials in dye sensitized solar cells (DSCs) to broaden the range of light absorption. However, the origin of the enhancements can be induced by both upconversion and size-dependent light scattering effects. To clarify the role of the upconversion material in the photoelectrode of DSCs, an upconversion induced device was realized here, which has the size-dependent light scattering effect eliminated via the application of NaYF4:Er3+, Yb3+@SiO2 upconversion nanoparticles (β-NYEY@SiO2 UCNPs). An enhancement of 6% in efficiency was observed for the device. This demonstration provided an insight into the possible further employment of upconversion in DSCs.
Co-reporter:Tao Peng, Weiwei Sun, Chengliang Huang, Wenjing Yu, Bobby Sebo, Zhigao Dai, Shishang Guo, and Xing-Zhong Zhao
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 1) pp:14
Publication Date(Web):December 17, 2013
DOI:10.1021/am404265q
The construction of nanoporous conductive polymer membranes has potential applications in catalysts and energy-conversion devices. In this letter, we present a facile method to prepare free-standing polypyrrole (PPy) nanotube films by simply heating pulp-like homogeneous suspensions at a low temperature, which can be employed as a novel counter electrode (CE) to substitute for the expensive fluorine-doped tin oxide (FTO) glass and Pt used in dye-sensitized solar cells (DSSCs). The DSSCs assembled with these paper-like PPy membranes show an impressive conversion efficiency of 5.27%, which is about 84% of the cell with a conventional Pt/FTO CE (6.25%).Keywords: counter electrode; dye-sensitized solar cells; free-standing; FTO- and Pt-free; polypyrrole nanotube membrane; self-assembled;
Co-reporter:Pingli Qin, Guojia Fang, Fei Cheng, Weijun Ke, Hongwei Lei, Haoning Wang, and Xingzhong Zhao
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 4) pp:2963
Publication Date(Web):February 7, 2014
DOI:10.1021/am405571a
Efficient organic solar cells (OSCs) based on regioregular of poly (3-hexylthiophene):fullerene derivative [6,6]-phenyl-C61butyric acid methyl ester composites have been fabricated on indium tin oxide (ITO) coated glass substrates by using a sputtered sulfur-doped molybdenum oxide (S-MoO3) film as anode interface layer (AIL). With the help of X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy, we find that oxygen flow ratio control can modulate the amount of sulfur doping into MoO3, then further tune the Mo+4/Mo+5/Mo+6 composition ratios, Fermi level, electron affinity, valence band ionization energy and band gap of MoO3. A partially occupied Mo 4d-bands of Mo5+ and Mo4+ states modulated by sulfur doping are the main factor which influences the valence electronic structure of S-MoO3.These orbitals overlap interrelation push the valence band close to S-MoO3’s Fermi level, thus make it into a p-type semiconductor. S-MoO3 with smaller ionization energy and electron affinity is better suitable as an efficient AIL. On the basis of these AILs, a photovoltaic power conversion efficiency up to 3.69% has been achieved, which is 12% higher than that in pure MoO3 AIL case. The result thus shows that sulfur doping is a useful method to modify anode interface layer for improving the hole-transport properties of MoO3, which can improve the device performances.Keywords: MoO3; anode interface layer; organic solar cell; sulfur doping; work function;
Co-reporter:Weiwei Sun, Tao Peng, Yumin Liu, Wenjing Yu, Kun Zhang, Hadja Fatima Mehnane, Chenghao Bu, Shishang Guo, and Xing-Zhong Zhao
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 12) pp:9144
Publication Date(Web):June 2, 2014
DOI:10.1021/am501233q
Layer-by-layer self-assembled TiO2 hierarchical nanosheets with exposed {001} facets have been successfully fabricated via a simple one-step solvothermal reaction. The anatase TiO2 layer-by-layer hierarchical nanosheets (TiO2 LHNs) exhibit favorable light scattering effect and large surface area, owing to their layer-by-layer hierarchical structure. When applied to the dye-sensitized solar cells (DSSCs), the layer-by-layer hierarchical structure with exposed {001} facet could effectively enhance light harvesting and dye adsorption, followed by increasing the photocurrent of DSSCs. As a result, the photoelectric conversion efficiency (η) of 7.70% has been achieved for the DSSCs using TiO2 LHNs as the bifunctional layer, indicating 21% improvement compared to the pure Degussa P25 (6.37%) as photoanode. Such enhancement can be mainly ascribed to the better light scattering capability of TiO2 LHNs, higher dye adsorption on TiO2 LHN {001} facets, and longer lifetime of the injected electrons in TiO2 LHNs compared to P25, which are examined by UV–vis spectrophotometry and electrochemical impedance spectroscopy under the same conditions. These remarkable properties of TiO2 LHNs make it a promising candidate as a bifunctional scattering material for DSSCs.Keywords: dye-sensitized solar cells; exposed {001} facets; favorable light scattering effect; long lifetime; TiO2 hierarchical nanosheets;
Co-reporter:Weiwei Sun, Tao Peng, Yumin Liu, Niu Huang, Shishang Guo, Xingzhong Zhao
Carbon 2014 Volume 77() pp:18-24
Publication Date(Web):October 2014
DOI:10.1016/j.carbon.2014.04.069
Due to the advantages of both rapid electron transport of reduced graphene oxide (rGO) sheet and high catalytic performance of ordered mesoporous carbon (OMC), composites of OMC with rGO (G@OMC) have been prepared through the hard-template approach and used as efficient counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). When compared with pure OMC, the as-obtained G@OMC composites exhibit a higher electrocatalytic activity for the reduction of triiodide, owing to the synergetic effect between rGO and OMC. As a consequence, the DSSCs assembled with this G@OMC (CE show an improved photovoltaic conversion efficiency of 6.38% compared with 5.67% for DSSCs assembled with OMC CE, which could compete with the efficiency (7.05%) produced by the Pt CE under the same conditions.
Co-reporter:Weiwei Sun, Kang Sun, Tao Peng, Sujian You, Haiming Liu, Liangliang Liang, Shishang Guo, Xing-Zhong Zhao
Journal of Power Sources 2014 Volume 262() pp:86-92
Publication Date(Web):15 September 2014
DOI:10.1016/j.jpowsour.2014.03.086
•We reported a facile one-pot approach to prepare TiO2 HFSs with exposed {001} facets.•The TiO2 HFSs exhibit superior light scattering and dye loading amount property.•This study provides a convenient route for the development of novel hierarchical TiO2.Hierarchical fastener-like spheres assembled from anatase TiO2 nanosheets with exposed {001} facets are successfully synthesized via a facile one-pot hydrothermal process. Compared with standard commercial P25, the as-obtained hierarchical fastener-like TiO2 spheres exhibit an improved light harvesting efficiency, owing to the excellent light scattering effect of layer-by-layer hierarchical structure and superior dye adsorption capacity of the dominant {001} facets. As a consequence, the photoanode composed of TiO2 fastener-like sphere scattering layer shows an improved DSSCs conversion efficiency of 7.01% compared to that of commercial P25 (5.78%). The remarkable electrochemical performances of hierarchical fastener-like TiO2 spheres indicate their promising application as scattering materials for DSSCs.In this work, hierarchical fastener-like spheres layer-by-layer assembled from anatase TiO2 nanosheets with exposed {001} facets have been successfully prepared via a facile one-pot hydrothermal process and used as an efficient scattering layer for dye-sensitized solar cells (DSSCs). DSSCs employing this TiO2 HFSs scattering layer achieve conversion efficiency as high as 7.01%, showing 21.3% increment over that derived from DSSCs with commercial P25 photoanode under the same conditions.
Co-reporter:Qinqin Huang;Bolei Chen;Rongxiang He;Zhaobo He;Bo Cai;Junhua Xu;Weiyi Qian;Helen Laiwa Chan;Wei Liu;Shishang Guo;Jikang Yuan
Advanced Healthcare Materials 2014 Volume 3( Issue 9) pp:1420-1425
Publication Date(Web):
DOI:10.1002/adhm.201300670
Co-reporter:Xiaohua Sun, Qiaoling Zhang, Yumin Liu, Niu Huang, Panpan Sun, Tao Peng, Tianyou Peng, Xing-Zhong Zhao
Electrochimica Acta 2014 Volume 129() pp:276-282
Publication Date(Web):20 May 2014
DOI:10.1016/j.electacta.2014.02.110
In-doped TiO2 thin film was introduced at the interface of fluorine-doped tin oxide (FTO) substrate and mesoporous TiO2 film by spin-coating method, and its application as a new compact layer material for dye-sensitized solar cells (DSSCs) was investigated. The scanning electron microscopy (SEM), UV-visible spectroscopy, current-voltage characteristics, Mott-Schottky analysis, electrochemical impedance spectroscopy (EIS) analysis and open-circuit voltage decay (OCVD) technique are used to characterize the morphology, optical transmittance and flat-band potentials (Vfb) of In-doped titania compact film and its effect to the photoelectron conversion process. It was found that In-doping increased the transmittance of TiO2 compact layer, the interfacial resistance between FTO substrate and porous TiO2 film and the flat-band potential of TiO2 film. The In-doped TiO2 compact layer effectively suppressed the charge recombination from FTO to the electrolyte, increased the optical absorption of dye and then increased the short-circuit photocurrent density (Jsc). Furthermore, In-doped TiO2 compact layer acted as a weak energy barrier, which increased the electron density in the mesoporous TiO2 film, thus improved open-circuit photovoltage (Voc). As a result, the overall energy conversion efficiency of the DSSC with In-doped TiO2 compact layer was enhanced by 11.9% and 6.9% compared to the DSSC without compact layer and with pure TiO2 compact layer, respectively. It indicated that In-doped TiO2 is a promising compact layer material for dye-sensitized solar cells.
Co-reporter:Zhengfu Tong ; Tao Peng ; Weiwei Sun ; Wei Liu ; Shishang Guo
The Journal of Physical Chemistry C 2014 Volume 118(Issue 30) pp:16892-16895
Publication Date(Web):March 24, 2014
DOI:10.1021/jp500412e
The novel concept of introducing intermediate band into the mesoporous TiO2 backbone of dye-sensitized solar cells (DSSCs) is proposed to take full advantage of the sunlight and enhance the power conversion efficiency. Nominal trace amount W-doped TiO2 nanocrystralline films were prepared with the purpose of forming intermediate band in the bandgap of TiO2. A notable improvement of the device performance was obtained when N-type W-doped TiO2 films were applied as the photoanode of DSSCs. The short-circuit current density (Jsc) increased from 12.40 mA cm–2 to 15.10 mA cm–2, and the conversion efficiency increased from 6.64 to 7.42% when nominal 50 ppm (ppm) W-doped TiO2 was adopted.
Co-reporter:Weiwei Sun, Tao Peng, Yumin Liu, Sheng Xu, Jikang Yuan, Shishang Guo and Xing-Zhong Zhao
Journal of Materials Chemistry A 2013 vol. 1(Issue 8) pp:2762-2768
Publication Date(Web):07 Jan 2013
DOI:10.1039/C2TA01000C
Hierarchically porous polyaniline–reduced graphene oxide hybrids have been developed via oxidative polymerization of aniline by MnO2 on reduced graphene sheets under acidic conditions (named M-PANI@rGO). The formation mechanism of the above hybrids indicates that the MnO2 undergoes oxidative disintegration and results in the porous structure of polyaniline (PANI) nanoparticle formation on the reduced graphene oxide (rGO) surface. The scanning electron microscopy (SEM) images and Brunauer–Emmett–Teller (BET) nitrogen sorption–desorption measurement clearly showed the nanoporous nature of the M-PANI@rGO hybrids. TEM-EDX confirmed the complete removal/degradation of MnO2 during the oxidative polymerization of aniline. Just for comparison, PANI–rGO hybrids have also been prepared via conventional polymerization using (NH4)2S2O8 as the oxidant (named C-PANI@rGO). When these different architectural PANI@rGO hybrids were applied as the counter electrode for dye-sensitized solar cells (DSSCs), the short-circuit current density (Jsc) and power-conversion efficiency (η) of the DSSCs with C-PANI@rGO hybrids are measured to be 11.64 mA cm−2 and 5.62%, respectively, while the corresponding values are 12.88 mA cm−2 and 6.15% for the DSSCs with M-PANI@rGO hybrids, which is comparable to 6.73% for the cell with a Pt counter electrode under the same experimental conditions. The hierarchically porous M-PANI@rGO hybrid is thus a promising candidate to replace platinum as a counter electrode for DSSCs.
Co-reporter:Tao Peng, Weiwei Sun, Xiaohua Sun, Niu Huang, Yumin Liu, Chenghao Bu, Shishang Guo and Xing-Zhong Zhao
Nanoscale 2013 vol. 5(Issue 1) pp:337-341
Publication Date(Web):05 Nov 2012
DOI:10.1039/C2NR32536E
Controlling over ordered porosity by self-assembly is challenging in the area of materials science. Materials with highly ordered aperture are favorable candidates in catalysis and energy conversion device. Here we describe a facile process to synthesize highly ordered mesoporous carbon (OMC) by direct tri-constituent co-assembly method, which uses resols as the carbon precursor, tri-block copolymer F127 as the soft template and tetraethoxysilane (TEOS) as the inorganic precursor. The obtained products are characterized by small-angle X-ray diffraction (SAXD), Brunauer–Emmett–Teller (BET) nitrogen sorption–desorption measurement and transmission electron microscope (TEM). The results indicate that the OMC possesses high surface areas of 1209 m2 g−1, homogeneous pore size of 4.6 nm and a large pore volume of 1.65 cm3 g−1. The advantages of high electrochemical active surface area and favorable accessible porosity of OMC benefit the catalysis of I3− to I−. As a result, the OMC counter electrode displays a remarkable property when it was applied in dye-sensitized solar cells (DSSCs). For comparison, carbon black (CB) counter electrode and Pt counter electrode have also been prepared. When these different counter electrodes were applied for dye-sensitized solar cells (DSSCs), the power-conversion efficiency (η) of the DSSCs with CB counter electrode are measured to be 5.10%, whereas the corresponding values is 6.39% for the DSSC with OMC counter electrode, which is comparable to 6.84% of the cell with Pt counter electrode under the same experimental conditions.
Co-reporter:Jun-Hua Xu, Fu-Ping Gao, Xue-Feng Liu, Qian Zeng, Shi-Shang Guo, Zhi-Yong Tang, Xing-Zhong Zhao and Hao Wang
Chemical Communications 2013 vol. 49(Issue 40) pp:4462-4464
Publication Date(Web):07 Mar 2013
DOI:10.1039/C3CC00304C
We demonstrate the on-chip preparation of size-controllable supramolecular gelatin nanoparticles (SGNs) with a quantum dot (QD) payload as matrix metalloproteinase (MMP) responsive cancer cell imaging probes.
Co-reporter:Liangliang Liang, Yumin Liu and Xing-Zhong Zhao
Chemical Communications 2013 vol. 49(Issue 38) pp:3958-3960
Publication Date(Web):25 Mar 2013
DOI:10.1039/C3CC41252K
Double-shell β-NaYF4:Yb3+, Er3+/SiO2/TiO2 submicroplates have been used as a scattering and upconverting layer for dye-sensitized solar cells (DSSCs). Due to their effective light scattering and upconverting effects, the performance of DSSCs was significantly enhanced, resulting in an efficiency of 7.70%, which is a noticeable improvement of ∼29.41% compared to the cell without the bifunctional layer (5.95%).
Co-reporter:Sihang Bai, Chenghao Bu, Qidong Tai, Liangliang Liang, Yumin Liu, Sujian You, Zhenhua Yu, Shishang Guo, and Xingzhong Zhao
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 8) pp:3356
Publication Date(Web):April 1, 2013
DOI:10.1021/am400337d
Bis(imidazolium) iodides (bis-Im+I–s) are synthesized with different substituents and used as electrolytes in dye-sensitized solar cells (DSSCs). Three kinds of low-volatility electrolytes are prepared by using 1,1′-methylene bis(3-imidazolium) diiodide (MIDI), 1,1′-methylene bis(3-n-methylimidazolium) diiodide (MMIDI), and 1,1′-methylene-bis(3-n-ethylimidazolium) diiodide (MEIDI) as the iodide sources. The effects of these substituents on the photovoltaic performance of the cells are investigated. It is found that the device shows a lower short-circuit photocurrent (Jsc), higher open-voltage (Voc) and fill factor (FF) with the increased cation size in electrolyte. These results are explained by electrostatic interactions between the solvated Im+ and the negatively charged species. Meanwhile, the explanation is supported by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), open circuit voltage decay (OCVD), and dark current measurements.Keywords: bis(imidazolium) iodide; dye-sensitized solar cells; electrostatic interaction; low-volatility electrolyte; triiodide/iodide redox couple;
Co-reporter:Chenghao Bu, Yumin Liu, Zhenhua Yu, Sujian You, Niu Huang, Liangliang Liang, and Xing-Zhong Zhao
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 15) pp:7432
Publication Date(Web):June 28, 2013
DOI:10.1021/am4017472
A facile in situ carbonization method was demonstrated to prepare the highly transparent carbon counter electrode (CE) with good mechanical stability for bifacial dye-sensitized solar cells (DSCs). The optical and electrochemical properties of carbon CEs were dramatically affected by the composition and concentration of the precursor. The well-optimized carbon CE exhibited high transparency and sufficient catalytic activity for I3– reduction. The bifacial DSC with obtained carbon CE achieved a high power conversion efficiency (PCE) of 5.04% under rear-side illumination, which approaches 85% that of front-side illumination (6.07%). Moreover, the device shows excellent stability as confirmed by the aging test. These promising results reveal the enormous potential of this transparent carbon CE in scaling up and commercialization of low cost and effective bifacial DSCs.Keywords: bifacial dye-sensitized solar cells; in situ carbonization method; long-term stability; optical and electrochemical properties; transparent carbon counter electrode;
Co-reporter:Chenghao Bu, Qidong Tai, Yumin Liu, Shishang Guo, Xingzhong Zhao
Journal of Power Sources 2013 Volume 221() pp:78-83
Publication Date(Web):1 January 2013
DOI:10.1016/j.jpowsour.2012.07.117
A novel transparent and stable polypyrrole (PPy) electrode that can properly serve as a counter electrode for the bifacial dye-sensitized solar cell (DSSC) has been prepared by in situ polymerization of pyrrole monomer on FTO glass. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurement show the considerable catalytic activity of PPy counter electrode. The photovoltaic parameters of bifacial DSSCs are strongly dependent on the initial monomer concentration of pyrrole. The optimized PPy counter electrode has been fabricated under the initial monomer concentration of 0.3 M, a bifacial DSSC based on this PPy electrode shows conversion efficiencies of 5.74% and 3.06% corresponding to front- and rear-side illumination, respectively. Compared to the conventional Pt-based DSSCs, the design of bifacial DSSC with transparent PPy counter electrode improves the utilization ratio of incident light. Moreover, the considerable conversion efficiency and the good long-term stability of PPy-based device demonstrated by the stability test highlight the potential large-scale commercial application of this transparent PPy counter electrode.Highlights► A transparent PPy film with electrochemical catalytic activity has been prepared. ► A bifacial DSSC based on this PPy film has been reported for the first time. ► The DSSC based on this PPy counter electrode shows excellent long-term stability. ► The application of this PPy film in DSSC would bring down the production cost.
Co-reporter:Bobby Sebo, Niu Huang, Yumin Liu, Qidong Tai, Liangliang Liang, Hao Hu, Sheng Xu, Xing-Zhong Zhao
Electrochimica Acta 2013 Volume 112() pp:458-464
Publication Date(Web):1 December 2013
DOI:10.1016/j.electacta.2013.08.167
Light harvesting in dye-sensitized solar cells (DSSCs) mediated by plasmonic metallic nanoparticles and sub-micron light-scattering metal oxides is a facile and cost-effective approach to achieving high device performance. Ag nanoparticles, protected by thin shells of TiO2, were incorporated in TiO2 photoanode. The large plasmonic near-field intensity generated by these nanoparticles caused an 18.3% rise in photocurrent, which resulted in an enhanced efficiency of 6.23% as compared to 5.29% efficiency of DSSC based on unmodified TiO2 photoanode. In addition, DSSC with TiO2 nanofibers (NFs) embedded in TiO2 photoanode was also constructed, which because of the efficient light scattering ability of the nanofibers, attained an efficiency of 7.14% as a result of a current rise of 36.9%. Another DSSC was assembled with Ag NPs added to the photoanode of the NFs-based DSSC to further boost cell performance. The addition of Ag NPs, however, did not produce an appreciable change in the cell performance. The reason for this unexpected outcome was probably due to the low internal resistance associated with charge recombination and large resistance to electron transport in the cell as determined by electrochemical impedance analysis computed in this work.
Co-reporter:Zhenhua Yu, Chenhao Bu, Ziyao Zhou, Yumin Liu, Niu Huang, Sihang Bai, Houqiang Fu, Shishang Guo, Xingzhong Zhao
Electrochimica Acta 2013 Volume 107() pp:695-700
Publication Date(Web):30 September 2013
DOI:10.1016/j.electacta.2013.06.125
A facile and reliable method is applied to prepare the electrolyte based on hydroquinone (HQ)/benzoquinone (BQ) redox couple for dye-sensitized solar cells (DSSCs) in open environment by adding moderate amount of acetic acid (HAc), and the best conversion efficiency (η) of 5.82% is achieved under 100 mW cm−2 (AM 1.5 G) illumination. Electrochemistry properties of DSSCs using such redox couple are measured and the results show a higher current and better charge transfer in contrast to I−/I3−. And a slightly higher efficiency of 5.88% is obtained when HQ and BQ are symmetrically substituted by two methyls. With advantages of high efficiency, compatible with the most common dye N719 and easily tuned by facile structural modification, the redox shuttle employing HQ/BQ via HAc treatment is very promising to be employed in efficient DSSCs.
Co-reporter:N. Huang, B. Sebo, M.M. Pan, Y.M. Liu, T. Peng, W.W. Sun, C.H. Bu, X.Z. Zhao
Solar Energy 2013 Volume 97() pp:266-272
Publication Date(Web):November 2013
DOI:10.1016/j.solener.2013.08.006
•We prepare 8–24 μm thick P25 films.•P25 films were prepared by coating one time.•P25 films were prepared by sintering one time.•The low-price of the paste has promising applications for industrial production.•P25 films have high light scattering ability and high-quality without cracking and delamination.A viscous TiO2 paste was prepared by ball-milling commercially available P25 with ethylene glycol and citric acid. The conventional three- or four-fold deposition process was replaced by a single coating-sintering step of TiO2 compound. That is coating the paste on Fluorine-doped SnO2 conductive glass, followed by sintering at high temperature. TiO2 films varying from 8 μm to 24 μm could be fabricated by this single coating-sintering step. The high viscosity of the paste, the esterification between ethylene glycol and citric acid and the subsequently polyester decomposition in the sintering process were the reasons to make high-quality thick film without cracking and delamination. 7.36% photoelectrical-conversion efficiency was achieved by using the photoelectrode with its P25 film thickness of 14.3 μm. Therefore, the paste would have promising applications for industrial production because of its low-price and simple process.
Co-reporter:Jun-Hua Xu, Fu-Ping Gao, Li-Li Li, Horse L. Ma, Yun-Shan Fan, Wei Liu, Shi-Shang Guo, Xing-Zhong Zhao, Hao Wang
Microporous and Mesoporous Materials 2013 Volume 182() pp:165-172
Publication Date(Web):1 December 2013
DOI:10.1016/j.micromeso.2013.08.050
•Drug-loaded mesoporous silica nanoparticles with gelatin corona (DOX⊂MSNs@Gel) were prepared.•Gelatin matrix on the MSNs surface can respond to matrix metalloproteinases overexpressed in the tumor environment.•DOX⊂MSNs@Gel is capable of enhancing tumor treatment efficacy and decreasing systemic toxicity against free drug.The matrix metalloproteinases (MMPs) are a family of proteases which are normally up-regulated in tumor tissues. Gelatin is a biocompatible and non-immunogenic substrate which can be degraded by MMPs. In this work, MMPs-degradable gelatin coated mesoporous silica nanoparticles (MSNs@Gel) were designed for endogenous tumor microenvironment-triggered release systems for cancer treatment in vivo. This drug delivery system is expected to attain preferential release of drugs in tumor microenvironment with diminished systemic toxicity. The gelatin corona can serve as both a protective layer for preventing drugs leakage and MMPs-digested substrates for responding the solid tumor microenvironment. Doxorubicin (DOX), as a model antitumor drug, was loaded into the mesopores of MSNs@Gel to give DOX⊂MSNs@Gel with controllable releasing feature upon the MMPs stimuli. Interestingly, the encapsulated DOX in the DOX⊂MSNs@Gel was barely delivered into the normal cells due to the less endocytosis activity compared to that of the cancerous cells, resulting in the decreased systemic toxicity and decreased side effect during the tumor treatment. Whilst in the tumor tissue, the gelatin layer of DOX⊂MSNs@Gel was degraded and the encapsulated DOX was released effectively. The released DOX was accumulated in the nucleus of tumor cells. In vivo studies demonstrated that the tumor growth of xenografted mice was significantly delayed without any appreciable body weight loss that indicated the lower systemic toxicity of DOX⊂MSNs@Gel compared to the free DOX.
Co-reporter:Rongxiang He;Libo Zhao;Yumin Liu;Nangang Zhang;Boran Cheng
Biomedical Microdevices 2013 Volume 15( Issue 4) pp:617-626
Publication Date(Web):2013 August
DOI:10.1007/s10544-013-9781-9
We demonstrate the isolation of circulating tumor cells (CTCs) with a biocompatible nano-film composed of TiO2 nanoparticles. Due to the enhanced topographic interaction between nano-film and cancer cell surface, cancer cells (HCT116) spiked into PBS and healthy blood can be recovered from the suspension, whose efficiencies were respectively 80 % and 50 %. Benifit from the biocompatibility of this nano-film, in-situ culture of the captured cancer cells is also available, which provides an alternative selection when the capture cell number was inadequate or the sample cannot be analyzed immediately. For the proof-of-concept study, we use this nano-film to separate the circulating tumor cells from the colorectal and gastric cancer patient peripheral blood samples and the captured CTCs are identified by a three-colored immunocytochemistry method. We investigated the cancer cells capture strength at the nano-bio interface through exposing the cells to fluid shear stress in microfluidic device, which can be utilized to increase the purity of CTCs. The result indicated that 50 % of the captured cells can be detached from the substrate when the fluid shear stress was 180 dyn cm−2. By integration of this CTCs capture nano-film with other single cell analysis device, we expected to further explore their applications in genome sequencing based on the captured CTCs.
Co-reporter:Yumin Liu, Haowei Zhai, Feng Guo, Niu Huang, Weiwei Sun, Chenghao Bu, Tao Peng, Jikang Yuan and Xingzhong Zhao
Nanoscale 2012 vol. 4(Issue 21) pp:6863-6869
Publication Date(Web):10 Sep 2012
DOI:10.1039/C2NR31954C
We demonstrate a strategy for incorporating plasmon resonant metallic nanoparticles in the construction of hierarchical TiO2 spheres. Localized electric fields can be produced by the addition of Au nanoparticles, which can excite dye molecules more effectively than incident far-field light. The synergistic effect of surface plasmon resonance with constructed TiO2 nanostructures has been investigated, and was confirmed by optical spectroscopy, J–V characteristics, EIS analysis and OCVD measurements. When Au nanoparticles are incorporated into the constructed TiO2 spheres, the device achieves a power conversion efficiency of 6.62%, a 4.6% increase compared to the device based on constructed TiO2 spheres without plasmon resonant Au nanoparticles, and a 17.4% increase compared to that without any treatment.
Co-reporter:Niu Huang, Yumin Liu, Tao Peng, Xiaohua Sun, Bobby Sebo, Qidong Tai, Hao Hu, Bolei Chen, Shi-shang Guo, Xingzhong Zhao
Journal of Power Sources 2012 Volume 204() pp:257-264
Publication Date(Web):15 April 2012
DOI:10.1016/j.jpowsour.2011.12.027
The interaction between ZnO compact layer and TiCl4 post-treatment on TiO2 photoelectrode for dye sensitized solar cell (DSSC) is investigated. Photoelectrode combined the two modifications is designated as ZnO + 2l + TiCl4. It is found that after the TiCl4 treatment the ZnO compact layer transforms to a bi-functional layer, which suppresses back electrons transfer from FTO to electrolyte and reduces the FTO/TiO2 interfacial resistance. In addition, the newly formed TiO2 coating generated by TiCl4 post-treatment contains abundant and well dispersed Zn element, which further facilitates electron transfer at TiO2 layer. Meanwhile, the electron lifetime in ZnO + 2l + TiCl4 is the longest. Consequently, the overall energy conversion efficiency of the cell with ZnO + 2l + TiCl4 is significantly enhanced to 8.9%, which is 8.8% higher than that with pure TiCl4 post-treatment and 17.7% higher than that without any treatment. These results are verified by material characterization and corresponding opto-electrical properties measurements. Experimental results demonstrate this facile method is a more promising alternative to the conventional interface and surface modification in high efficient DSSCs.Graphical abstractHighlights► We combined a basic ZnO compact layer with an acid TiCl4 post-treatment. ► The FTO/TiO2 interfacial resistance has been reduced when comparing with single treatment and untreated photoelectrodes. ► The newly formed TiO2 coating by the combined modification contained abundant and well dispersed Zn element. ► The photoelectrode with the combined modification has the lowest resistance for electron transport and the longest electron lifetime for recombination. ► The overall energy conversion efficiency was highly enhanced by the combined modification.
Co-reporter:Weiwei Sun, Xiaohua Sun, Tao Peng, Yumin Liu, Hongwei Zhu, Shishang Guo, Xing-zhong Zhao
Journal of Power Sources 2012 Volume 201() pp:402-407
Publication Date(Web):1 March 2012
DOI:10.1016/j.jpowsour.2011.10.097
Highly porous carbon/SnO2/TiO2 nanocomposite films that can be used as counter electrodes in dye-sensitized solar cells (DSSCs) are fabricated by coating a homogeneous and viscous carbon paste on F-doped tin oxide conducting glass. The carbon paste is prepared by ball-milling a mixture of carbon, SnO2 powder and TiO2 hydrosol in an organic solution. The composite films are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, Brunauer–Emmett–Teller and Form Talysruf Profiler. The results indicate that the photovoltaic performances of the composite DSSCs are influenced by the content of SnO2. When the content is increased to 30%, SnO2 not only acts as “framework” to strengthen the mechanical stability of the composite film but also increases the specific surface area and root-mean-square roughness, which improve fill factor and short-circuit current, finally increasing power conversion efficiency from 5.12% to 6.15%. Cyclic voltammetry analysis and electronic impedance spectroscopy of the optimum composite film display higher catalytic activity for I3−/I− redox reactions and much lower charge-transfer resistance compared with Pt, respectively. Dye-sensitized solar cells based on this nanocomposite counter electrode achieve efficiency as high as 6.15% which is comparable to that of the cells using sputtering Pt as counter electrode at similar conditions.Highlights► Dye-sensitized solar cells (DSSCs) based on low cost mesoporous carbon/SnO2/TiO2 nanocomposite counter electrode were fabricated. ► SnO2 could act as framework to strengthen the mechanical stability of the composite film. ► The content of SnO2 influenced the photoelectric performance of the composite DSSCs. ► The nanocomposite electrode with SnO2 content of 30% showed the highest power conversion efficiency. ► The optimum counter electrode revealed higher catalytic activity and lower Rct than Pt counter electrode.
Co-reporter:Bo-Lei Chen, Hao Hu, Qi-Dong Tai, Nan-Gang Zhang, Feng Guo, Bobby Sebo, Wei Liu, Ji-Kang Yuan, Jian-Bo Wang, Xing-Zhong Zhao
Electrochimica Acta 2012 Volume 59() pp:581-586
Publication Date(Web):1 January 2012
DOI:10.1016/j.electacta.2011.11.036
This paper reports an inverted fabrication process for the photoanode of a flexible dye sensitized solar cell (DSSC). This procedure involves assembling a free-standing TiO2 nanowires/nanoparticles hybrid membrane, via high temperature annealing, sputtering an indium tin oxide (ITO) layer onto this membrane, and transferring these onto a polydimethylsiloxane (PDMS) substrate. The inverted procedure prevents thermal decomposition of polymer substrate, whilst enabling effective thermal treatment of the functionalized titanium oxide. The flexible DSSC fabricated in this way has an efficiency of 2.7%, which is comparable with rigid device constructed using similar materials.
Co-reporter:Xiaohua Sun, Yumin Liu, Qidong Tai, Bolei Chen, Tao Peng, Niu Huang, Sheng Xu, Tianyou Peng, and Xing-Zhong Zhao
The Journal of Physical Chemistry C 2012 Volume 116(Issue 22) pp:11859-11866
Publication Date(Web):May 17, 2012
DOI:10.1021/jp211838g
Submicrometer-sized monodispersed TiO2 spheres were synthesized by a controlled hydrolysis of titanium tetraisopropoxide (TTIP) and subsequent solvothermal treatment. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible spectroscopy analyses revealed that aqueous ammonia concentration and calcining temperature significantly influence the morphology, crystallization, dye loading, and light scattering capacity of TiO2 microspheres. And it was found that the TiO2 microspheres prepared by this method showed a good thermal stability of phase. Bilayered dye-sensitized solar cells (DSSCs) composed of TiO2 microspheres as the scattering cover layers and TiO2 nanocrystallines as the underlayer exhibited a remarkable improvement in the power conversion efficiency (8.25%) compared with the nanocrystalline TiO2 DSSC (6.38%), owing to high light scattering efficiency and the dye-loading capacity of the microsphere cover layer. In addition, electrochemical impedance spectra (EIS) and open-circuit photovoltage decay curves (OCVD) testing indicated that the microsphere cover layer passivated the surface states, increased the density of bulk traps, enlarged the lifetime of electrons, and promoted more efficient charge-transfer, which was also an important reason for the improved power conversion efficiency of double-layered DSSCs.
Co-reporter:Kan Liu;Yuliang Deng;Nangang Zhang;Sizhe Li
Microfluidics and Nanofluidics 2012 Volume 13( Issue 5) pp:761-767
Publication Date(Web):2012 November
DOI:10.1007/s10404-012-0998-3
We report a droplet-based microfluidic synthetic technique to generate disk-like hydrogel beads for cell encapsulation and manipulation. Utilizing this microfluidic synthetic technique, the size of the disk-like calcium alginate (CA) hydrogel beads and the number of cells encapsulated in the disk-like CA hydrogel beads could be well controlled by individually adjusting the flow rates of reagents. As a proof-of-concept, we demonstrated that single cell (yeast cell or mammalian cell) could be successfully encapsulated into disk-like CA hydrogel beads with high cell viability. Taking advantage of the flat top/bottom surfaces of disk-like CA hydrogel beads, cell division processes in culture media were clearly observed and recorded at a desired position without rolling and moving. This facile microfluidic chip provides a feasible method for size-controlled disk-like hydrogel beads generation and cell encapsulation. It could be a promising candidate for cell division observation and quantitative biological study in lab-on-a-chip applications.
Co-reporter:Xing-Hu Ji, Nan-Gang Zhang, Wei Cheng, Feng Guo, Wei Liu, Shi-Shang Guo, Zhi-Ke He and Xing-Zhong Zhao
Journal of Materials Chemistry A 2011 vol. 21(Issue 35) pp:13380-13387
Publication Date(Web):03 Aug 2011
DOI:10.1039/C1JM12253C
In this paper we describe a versatile microfluidic strategy for simultaneous preparation of quantum dot-encoded microbeads with controllable barcodes. This method involves the generation of multiple dispersed solutions carrying stepwise concentration gradients of quantum dots by using a pyramidal microfluidic network, the formation of corresponding droplets in parallel flow-focusing droplet generators, and on-chip solidification of these droplets into microbeads. Using a designed microfluidic device, we simultaneously generated five kinds of fluorescence-encoded alginate hydrogel microbeads with a five-level stepwise concentration gradient of monochromatic quantum dot or five controllable ratios of two different-sized quantum dots. This method has the following features: (1) the barcode adapter compartment substitutes the respective preparation of precursor solutions containing the correct concentrations and ratios of different quantum dots for corresponding barcodes. (2) Identical microbeads with distinct quantum dot barcodes can be simultaneously generated in homogeneous conditions. (3) The microfluidic device can be upgraded by increasing or decreasing the inlets and outlets of the pyramidal network and the number of the parallel flow-focusing droplet generators to meet the requirements for the particular barcodes. We expect that this microfluidic route will facilitate the construction and mass-production of robust and reproducible barcode materials.
Co-reporter:Yuliang Deng, Nangang Zhang, Libo Zhao, Xiaolei Yu, Xinghu Ji, Wei Liu, Shishang Guo, Kan Liu and Xing-Zhong Zhao
Lab on a Chip 2011 vol. 11(Issue 23) pp:4117-4121
Publication Date(Web):19 Oct 2011
DOI:10.1039/C1LC20494G
In this paper, we demonstrate a new type of microfluidic chip that can realize continuous-flow purification of hydrogel beads from a carrier oil into aqueous solution by using a laminar-like oil/water interface. The microfluidic chip is composed by two functional components: (1) a flow-focusing bead generation module that can control size and shape of beads, (2) a bead extraction module capable of purifying hydrogel beads from oil into aqueous solution. This module is featured with large branch channels on one side and small ones on the opposite side. Water is continuously infused into the bead extraction module through the large branch channels, resulting in a laminar-like oil/water interface between the branch junctions. Simulation and experimental data show that the efficiency of oil depletion is determined by the relative flow rates between infused water and carrier oil. By using such a microfluidic device, viable cells (HCT116, colon cancer cell line) can be encapsulated in the hydrogel beads and purified into a cell culture media. Significantly improved cell viability was achieved compared to that observed by conventional bead purification approaches. This facile microfluidic chip could be a promising candidate for sample treatment in lab-on-a-chip applications.
Co-reporter:Xing-Hu Ji, Wei Cheng, Feng Guo, Wei Liu, Shi-Shang Guo, Zhi-Ke He and Xing-Zhong Zhao
Lab on a Chip 2011 vol. 11(Issue 15) pp:2561-2568
Publication Date(Web):17 Jun 2011
DOI:10.1039/C1LC20150F
Optical barcoding technology based on quantum dot (QD)-encoded microparticles has attracted increasing attention in high-throughput multiplexed biological assays, which is realized by embedding different-sized QDs into polymeric matrixes at precisely controlled ratios. Considering the advantage of droplet-based microfluidics, producing monodisperse particles with precise control over the size, shape and composition, we present a proof-of-concept approach for on-demand preparation of QD-encoded microparticles based on this versatile new strategy. Combining a flow-focusing microchannel with a double T-junction in a microfluidic chip, biocompatible QD-doped microparticles were constructed by shearing sodium alginate solution into microdroplets and on-chip gelating these droplets into a hydrogel matrix to encapsulate CdSe/ZnS QDs. Size-controllable QD-doped hydrogel microparticles were produced under the optimum flow conditions, and their fluorescent properties were investigated. A novel multiplex optical encoding strategy was realized by loading different sized QDs into a single droplet (and thus a hydrogel microparticle) with different concentrations, which was triggered by tuning the flow rates of the sodium alginate solutions entrapped with different-colored QDs. A series of QD-encoded microparticles were controllably, and continuously, produced in a single step with the present approach. Their application in a model immunoassay demonstrated the potential practicability of QD-encoded hydrogel microparticles in multiplexed biomolecular detection. This simple and robust strategy should be further improved and practically used in making barcode microparticles with various polymer matrixes.
Co-reporter:Ying Yang, Hao Hu, Cong-Hua Zhou, Sheng Xu, Bobby Sebo, Xing-Zhong Zhao
Journal of Power Sources 2011 Volume 196(Issue 4) pp:2410-2415
Publication Date(Web):15 February 2011
DOI:10.1016/j.jpowsour.2010.10.067
Quasi-solid state dye-sensitized solar cells (DSSCs) are fabricated with a novel polysaccharide gel electrolyte composed of agarose in 1-methyl-2-pyrrolidinone (NMP) as polymer matrix, lithium iodide (LiI)/iodine (I2) as redox couple and titania nanoparticles as fillers. The polysaccharide electrolyte with different agarose concentrations (1–5 wt%) and various inorganic filler TiO2 concentrations (0–10 wt%) are studied systematically by differential scanning calorimetry (DSC) and the AC impedance spectra. The electrochemical and photoelectric performances of DSSCs with these electrolytes are also investigated. It is found that increasing agarose and inorganic filler concentration leads to a decrease in Tg in the range of 1–2 wt% for agarose and 0–2.5 wt% for TiO2 changed electrolytes, which results in high conductivity in these electrolytes. From the electrochemical analysis, it is observed that the electron lifetime in TiO2 of DSSCs increases with agarose, while decreases with inorganic filler contents. The prolonged electron lifetime in DSSCs is advantageous to improve open-circuit voltage (Voc). Based on these results, the cell with the electrolyte of 2 wt% agarose shows the optimized energy conversion efficiency of 4.14%. The optimized efficiency of the DSSC with added titania is 4.74% at 2.5 wt% titania concentration.
Co-reporter:Yumin Liu, Xiaohua Sun, Qidong Tai, Hao Hu, Bolei Chen, Niu Huang, Bobby Sebo, Xing-zhong Zhao
Journal of Power Sources 2011 Volume 196(Issue 1) pp:475-481
Publication Date(Web):1 January 2011
DOI:10.1016/j.jpowsour.2010.07.031
A novel and thin ZnO compact blocking film is employed at the interface of fluorine-doped tin oxide (FTO) substrate and mesoporous TiO2, and its influence on dye-sensitized solar cells (DSSCs) is investigated. The ZnO film prepared by spin-coating method on FTO is characterized by energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and UV–vis spectrophotometer. The ZnO film is firstly employed as an energy barrier between FTO and mesoporous TiO2 film in DSSCs, which improves open-circuit photovoltage (Voc) and fill factor (FF) with compensation of Jsc decrease, finally increasing energy conversion efficiency from 5.85% to 6.70%. Electrochemical impedance spectra (EIS) analysis and open-circuit voltage decay (OCVD) technique reveal that the existence of the energy barrier not only resulted in the effect of suppressing back electrons transfer from FTO to electrolyte but also blocking the electrons injection from the conductive band of TiO2 to FTO. The former effect effectively reduces the recombination which occurs in the region of FTO substrate, and the latter leads to remarkable increment of electron density in the TiO2, thus resulting in enhanced Voc and FF. These results suggest that the methodology of introducing the semiconductor with a more negative conduction band edge than TiO2 as the compact blocking film in DSSCs may be feasible.
Co-reporter:Sheng Xu, Hao Hu, Bobby Sebo, Bolei Chen, Qidong Tai, Xingzhong Zhao
Journal of Power Sources 2011 Volume 196(Issue 24) pp:10817-10821
Publication Date(Web):15 December 2011
DOI:10.1016/j.jpowsour.2011.09.015
A convenient way is experimented to reduce the amount of dye in quasi-solid DSSCs but raise open-circuit photovoltage and photocurrent density. AFM stereoscopic morphology and calculated roughness of root mean square indicates looser porous configuration is formed in the modified TiO2 film which is beneficial for the penetration of quasi-solid electrolyte. Decreased content of sensitized dye is confirmed by UV–vis absorption spectra. Electrochemical impedance spectroscopy is employed to characterize the transport and recombination of electrons and also to assess the penetration of quasi-solid electrolyte in the porous matrix of DSSCs. Analysis of charge-transfer resistance and dc resistance of impedance of diffusion of tri-iodide reveals enhanced mobility of tri-iodide in DSSCs. Photovoltaic parameters of quasi-solid DSSCs show an increased open-circuit photovoltage due to the enlarged photoelectrode film porosity and the shift of redox level. Better penetration of quasi-solid electrolyte has a predominant advantage over the negative effect caused by lose of photocurrent, to some extent, as a result of decreased adsorbed dye. The best result of this beneficial outcome occurs when the PEG loading is 20%, giving an overall cell efficiency of 5.1%.Highlights► We demonstrated a convenient method of adding PEG in TiO2 paste to reduce the amount of dye in DSSCs but raise the open-circuit photovoltage and the photocurrent density. ► The photoelectrode form looser porous configuration which is benefitial for the penetration of electrolyte. ► The amount of dye decreased directly as the amount of PEG increased in the TiO2 paste. ► EIS indicates enhanced mobility of tri-iodide in the DSSCs. ► Raised open-circuit photovoltage is caused by enlarged photoelectrode film porosity and the shift of redox level.
Co-reporter:Hao Hu, Bo-Lei Chen, Cheng-Hao Bu, Qi-Dong Tai, Feng Guo, Sheng Xu, Jun-Hua Xu, Xing-Zhong Zhao
Electrochimica Acta 2011 Volume 56(Issue 24) pp:8463-8466
Publication Date(Web):1 October 2011
DOI:10.1016/j.electacta.2011.07.035
This study describes a systematic investigation of the stability of a carbon/TiO2 counter electrode for use in dye-sensitized solar cells (DSSCs). In this system, nanoparticle additives were introduced by adding Ti-hydrogel. The additives then bound carbon particles and enhanced the adhesion of carbon materials to the conductive substrate. After introducing the Ti-hydrogel into the carbon paste, the carbon/Ti-hydrogel composited counter electrode (HC-CE) showed a better conductivity and stability compared with that of the carbon counter electrode (C-CE), while the catalytic activity was not influenced. The device based on the HC-CE showed superior power conversion efficiency (6.3%) and long-term stability over the device based on the C-CE (5.8%).
Co-reporter:Yumin Liu, Xiaohua Sun, Qidong Tai, Hao Hu, Bolei Chen, Niu Huang, Bobby Sebo, Xing-Zhong Zhao
Journal of Alloys and Compounds 2011 Volume 509(Issue 37) pp:9264-9270
Publication Date(Web):15 September 2011
DOI:10.1016/j.jallcom.2011.07.018
An effective ZnO compact film (ZCF) has been introduced at the interface of fluorine doped tin oxide (FTO) substrate and mesoporous TiO2 layer, and its effect on dye-sensitized solar cells (DSSCs) has been compared to that of conventional TiO2 compact film (TCF). The ZCF and TCF prepared by spin-coating method on FTO are characterized by energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and UV–vis spectrophotometer. The existence of TiO2 can suppress the recombination occurring at the interface of FTO/electrolyte, resulting in a higher Jsc and Voc than bare FTO. The ZCF creates an energy barrier between FTO substrate and mesoporous TiO2 layer, which not only reduces the electron back transfer from FTO to I3− in the electrolyte, but also leads to the accumulation of photogenerated electrons, and increases the electron density in the conduction band of TiO2. The device based on FTO/ZCF substrate remarkably improves Voc and FF, finally increases energy conversion efficiency by 13.1% compared to the device based on bare FTO and 4.7% compared to the counterpart based on FTO/TCF.Highlights► ZnO has been introduced as the compact layer in dye-sensitized solar cells by a facile spin-coating method. ► The influences of ZnO and TiO2 compact films to photoelectron conversion process have been systematically investigated. ► The duel effect to photoelectron conversion process of ZnO compact film has been found. ► A new methodology of introducing an energy barrier at FTO/TiO2 interface rather than the surface of TiO2 electrode has been brought up.
Co-reporter:Sheng Xu, Cong-hua Zhou, Ying Yang, Hao Hu, Bobby Sebo, Bo-lei Chen, Qi-dong Tai, and Xingzhong Zhao
Energy & Fuels 2011 Volume 25(Issue 3) pp:1168
Publication Date(Web):February 7, 2011
DOI:10.1021/ef101546a
Solvent, dispersant, and surfactant play different roles in forming porous films of dye-sensitized solar cells (DSSCs) when they are added into the paste. We investigate the influence of ethanol, acetylacetone, and Triton-X100 on the photoelectrode of DSSCs with orthogonal array design experiments. Stereoscopic morphologies of photoelectrodes scanned with atomic force microscopy (AFM) show that decreasing the amount of ethanol in TiO2 paste results in forming a more compact structure of the photoelectrode for DSSCs. The TiO2 photoeletrode made with 2.5 g of TiO2 nanoparticle powder dissolved in 20 mL of ethanol presents lower root-mean-square (rms) roughness calculated from AFM, and its corresponding performance in DSSCs shows higher photoelectric conversion efficiency, while the effects of acetylacetone and Triton-X100 on the performance of DSSCs are not very apparent. Optimized photoelectrode dyed with N719 shows increased light absorption. This may result from adsorbing more amount of dye on a larger inner area of the porous photoelectrode. We find that the DSSC with the photoelectrode made from 2.5 g of TiO2 nanoparticle powder dissolved in 20 mL of ethanol containing 0.8 mL of acetylacetone and 0.6 mL of Triton-X100 shows a large increase in short-circuit current density (Jsc) and a little improvement in open-circuit voltage (Voc). At the optimized point, photoelectric conversion efficiency of 6.1% is obtained.
Co-reporter:Qidong Tai, Bolei Chen, Feng Guo, Sheng Xu, Hao Hu, Bobby Sebo, and Xing-Zhong Zhao
ACS Nano 2011 Volume 5(Issue 5) pp:3795
Publication Date(Web):April 6, 2011
DOI:10.1021/nn200133g
Highly uniform and transparent polyaniline (PANI) electrodes that can be used as counter electrodes in dye-sensitized solar cells (DSSCs) were prepared by a facile in situ polymerization method. They were used to fabricate a novel bifacially active transparent DSSC, which showed conversion efficiencies of 6.54 and 4.26% corresponding to front- and rear-side illumination, respectively. Meanwhile, the efficiency of the same photoanode employing a Pt counter electrode was 6.69%. Compared to conventional Pt-based DSSCs, the design of the bifacial DSSC fabricated in this work would help to bring down the cost of energy production due to the lower cost of the materials and the higher power-generating efficiency of such devices for their capabilities of utilizing the light from both sides. These promising results highlight the potential application of PANI in cost-effective, transparent DSSCs.Keywords: bifacial dye-sensitized solar cell; cost-effective; counter electrode; polyaniline; transparent
Co-reporter:Li-Bo Zhao;Si-Zhe Li;Hao Hu;Zhi-Xiao Guo;Feng Guo
Microfluidics and Nanofluidics 2011 Volume 10( Issue 2) pp:453-458
Publication Date(Web):2011 February
DOI:10.1007/s10404-010-0673-5
We reported a novel method to fabricate both spherical and nonspherical PDMS (Polydimethylsiloxane) particles of amphiphilic property. PDMS particles were first obtained using microfluidic devices. A layer of PAA (poly (acrylic acid)) polymer was then selectively grafted on a section of particle surface. After modification, PDMS particles exhibited an amphiphilic property. We demonstrated the assembly of spherical particles at the water/oil interface as well as the deformation of cuboidal particles which possessed a bowl-shaped structure after deformation.
Co-reporter:Zhi-Xiao Guo, Qian Zeng, Meng Zhang, Long-Ye Hong, Yang-Feng Zhao, Wei Liu, Shi-Shang Guo, Xing-Zhong Zhao
Sensors and Actuators A: Physical 2011 Volume 172(Issue 2) pp:546-551
Publication Date(Web):December 2011
DOI:10.1016/j.sna.2011.09.019
A valve-based microfluidic micromixer was developed for multiply component droplets generation, manipulation and active mixing. By integrating pneumatic valves in microfluidic device, droplets could be individually generated, merged and well mixed automatically. Moreover, droplet volume could be controlled precisely by tuning loading pressure or the flow rate of the oil phase, and certain droplets fusion conditions were also investigated by adjusting the droplet driving times and oil flow rates. In these optimized conditions, fluorescence enhancement of droplets was used to detect Hg (II) ions in droplet by mixing with probe droplets (Rhodamine B quenched by gold nanoparticle). This method would have powerful potential for tiny volume sample assay or real-time chemical reaction study.
Co-reporter:Lu Peng;Min Yang;Shi-shang Guo;Wei Liu
Biomedical Microdevices 2011 Volume 13( Issue 3) pp:559-564
Publication Date(Web):2011 June
DOI:10.1007/s10544-011-9526-6
Interfacial tension plays an important role in microfluidic emulsification, which is the process of preparing emulsions. A promising method which controls droplet behavior according to the function of the interfacial tension in the process of microfluidic emulsification is reported. The droplet size and generation frequency changed regularly to obtain appropriate concentrations of surfactant. This method could be of great help for setting up the size-controllable droplet generation systems, and ameliorating the emulsification technology. The interfacial tension effect was first analyzed by computational simulation before the real experiment, which significantly improved the efficiency of the whole research process.
Co-reporter:Hong-Wei Zhu;Nan-Gang Zhang;Rong-Xiang He;Shi-Ze Li
Microfluidics and Nanofluidics 2011 Volume 10( Issue 6) pp:1343-1349
Publication Date(Web):2011 June
DOI:10.1007/s10404-010-0761-6
We report a feasible method that can precisely control the fission of droplets by modulating the flow resistance using pneumatic valves. Multilayer soft lithography was used to fabricate the valves. They can be used as variable microfluidic resistor (VMR) to dramatically change the flow resistance. A simulation has been done to forecast the behavior of droplets. We used this technique to control break-up of generated droplets and direct their motion. Droplets with different volume ratios were obtained in one chip. To investigate the mechanism, an equivalent electrical circuit was introduced to compare with the fluid network. This method could potentially be applied to different geometries, especially for the microfluidic network consisting of a set of two parallel channels with a common inlet and different outlets in bifurcating channels. Besides, manipulation of bubbles was also demonstrated.
Co-reporter:Zuci Quan, Dan Li, Bobby Sebo, Wei Liu, Shishang Guo, Sheng Xu, Huiming Huang, Guojia Fang, Meiya Li, Xingzhong Zhao
Applied Surface Science 2010 Volume 256(Issue 11) pp:3669-3675
Publication Date(Web):15 March 2010
DOI:10.1016/j.apsusc.2010.01.005
Abstract
Zn0.95−xCo0.05CuxO (ZCCO, where x = 0, 0.005, 0.01 and 0.015) thin films were deposited on Si (1 0 0) substrates by pulsed laser deposition technique. Crystal structures, surface morphologies, chemical compositions, bonding states and chemical valences of the corresponding elements for ZCCO films were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS). XRD and FESEM results indicate that crystallite sizes of the highly (0 0 2)-oriented ZCCO films slightly decrease with increasing Cu content. When the Cu content increases from 0 to 0.015, Zn 2p3/2, Co 2p, Cu 2p3/2 and O 1s peaks of the ZCCO film shift towards higher or lower binding energy regions, and the reasons for these chemical shifts are investigated by fitting the corresponding XPS narrow-scan spectra. Both in-plane and out-of-plane magnetization-magnetic field hysteresis loops of the ZCCO films reveal that all the films have room temperature ferromagnetisms (RTFMs). The conceivable origin of the RTFM is ascribed to the combined effects of the local structural disorder resulted from (Co2+, Cu2+, Cu1+)-cations which substitute Zn2+ ions in the ZnO matrices, ferromagnetic coupling between coupled dopant atoms caused by Co2+ (3d74s0) and Cu2+ (3d94s0) spin states, and exchange interactions between the unpaired electron spins originating from lattice defects induced by Cu doping in the Zn0.95Co0.05O matrices.
Co-reporter:Cong-hua Zhou, Ying Yang, Jing Zhang, Sheng Xu, Su-juan Wu, Hao Hu, Bo-lei Chen, Qi-dong Tai, Zhen-hua Sun, Xing-zhong Zhao
Electrochimica Acta 2009 Volume 54(Issue 23) pp:5320-5325
Publication Date(Web):30 September 2009
DOI:10.1016/j.electacta.2008.12.058
Counterelectrode plays an important role in dye sensitized solar cells. It helps the regeneration of the redox couples in electrolyte and makes the cell a complete circuit. In order to improve the electrochemical performance of counterelectrode, a strategy of sandblasting has been utilized to pre-treat the surface of glass substrate. Counterelectrodes were fabricated by sputtering Pt/Ti bilayers films onto the treated substrates. Morphological, electrical, electrochemical and optical properties of the counterelectrode were characterized by scanning electronic microscopy, four-probe measurement, electrochemical impedance spectroscopy, cyclic voltammetry and UV–vis reflection spectroscopy, respectively. Effect of the treatment on these properties was evaluated. It was found that counterelectrode made from sandblasted substrates showed increased roughness of surface and sheet resistance, along with the enhanced catalysis efficiency and improved light scattering. The enhanced catalysis efficiency toward reduction of tri-iodide was found to be due to smaller Pt crystallite grown on the sandblasted substrate, since the electrochemical active surface area changed little. And scattering was caused by increased roughness of the substrate. Typical solar cells were assembled with the counterelectrode made of the sandblasted substrates. Effect of the treatment on current–voltage curves and performance parameters of the solar cells was checked and discussed.
Co-reporter:Sujuan Wu, Hongwei Han, Qidong Tai, Jing Zhang, Sheng Xu, Conghua Zhou, Ying Yang, Hao Hu, BoLei Chen, Xing-zhong Zhao
Journal of Power Sources 2008 Volume 182(Issue 1) pp:119-123
Publication Date(Web):15 July 2008
DOI:10.1016/j.jpowsour.2008.03.054
A novel surface modification method was carried out by reactive dc magnetron sputtering to fabricate TiO2 electrodes coated with Al2O3 for improving the performance of dye-sensitized solar cells (DSSCs). The Al2O3-coated TiO2 electrodes had been characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–vis spectrophotometer, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The study results revealed that the modification to TiO2 increases dye absorption amount, reduces trap sites on TiO2, and suppresses interfacial recombination. The impact of sputtering time on photoelectric performance of DSSCs was investigated. Sputtering Al2O3 for 4 min on 5-μm thick TiO2 greatly improves all cell parameters, resulting in enhancing the conversion efficiency from 3.93% to 5.91%. Further increasing sputtering time decreases conversion efficiency.
Co-reporter:Huiming Huang, Yangjun Ou, Sheng Xu, Guojia Fang, Meiya Li, X.Z. Zhao
Applied Surface Science 2008 Volume 254(Issue 7) pp:2013-2016
Publication Date(Web):30 January 2008
DOI:10.1016/j.apsusc.2007.08.041
Abstract
Highly transparent conductive Dy2O3 doped zinc oxide (ZnO)1–x(Dy2O3)x nanocrystalline thin films with x from 0.5% to 5% have been deposited on glass substrate by pulsed laser deposition technique. The structural, electrical and optical properties of Dy2O3 doped thin films were investigated as a function of the x value. The experimental results show that the Dy concentration in Dy-doped ZnO thin films has a strong influence on the material properties especially electrical properties. The resistivity decreased to a minimum value of 5.02 × 10−4 Ω cm with x increasing from 0.5% to 1.0%, then significantly increased with the further increasing of x value. On the contrary, the optical direct band gap of the (ZnO)1–x(Dy2O3)x films first increased, then decreased with x increasing. The average transmission of Dy2O3 doped zinc oxide films in the visible range is above 90%.
Co-reporter:Jing Zhang;Hongwei Han;Sheng Xu;Sujuan Wu;Conghua Zhou;Ying Yang ;Xingzhong Zhao
Journal of Applied Polymer Science 2008 Volume 109( Issue 2) pp:1369-1375
Publication Date(Web):
DOI:10.1002/app.28208
Abstract
A quasi-solid-state electrolyte for the dye-sensitized solar cells was prepared following the phase inversion process. The microporous polymer electrolyte based on poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) hybrid with different amount of TiO2 nanoparticles were prepared. The surface morphologies, the differential scanning calorimetry, and the ionic conductivity of the microporous polymer electrolyte were tested and analyzed. The results indicated that the microporous polymer electrolyte with TiO2 nanoparticles modification exhibited better ionic conductivity compared with the original P(VDF-HFP) polymer electrolyte. The optimal ionic conductivity of 0.8 mS cm−1 is obtained with the 30 wt % TiO2 nanoparticles modification. When assembled with the 30 wt % TiO2 nanoparticles modified quasi-solid-state electrolyte, the dye-sensitized TiO2 nanocrystalline solar cell exhibited the light to electricity conversion efficiency of 2.465% at light intensity of 42.6 mW cm−2, much better than the performance of original P(VDF-HFP) microporous polymer electrolyte DSSC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Ying Yang, Jing Zhang, Conghua Zhou, Sujuan Wu, Sheng Xu, Wei Liu, Hongwei Han, Bolei Chen and Xing-zhong Zhao
The Journal of Physical Chemistry B 2008 Volume 112(Issue 21) pp:6594-6602
Publication Date(Web):May 6, 2008
DOI:10.1021/jp801156h
The effect of lithium iodide concentration on the conduction behavior of poly(ethylene oxide)−poly(vinylidene fluoride) (PEO−PVDF) polymer-blend electrolyte and the corresponding performance of the dye-sensitized solar cell (DSSC) were studied. The conduction behavior of these electrolytes was investigated with varying LiI concentration (10−60 wt % in polymer blend) by impedance spectroscopy. A “polymer-in-salt” like conduction behavior has been observed in the high salt concentration region. The transition from “salt-in-polymer” to “polymer-in-salt” conduction behavior happened at the salt content of 23.4 wt %, which is much lower than 50 wt % as generally reported. The electrolyte shows the highest ionic conductivity (∼10−3 S cm−1) at the salt concentration above 23.4 wt %. From the evaluation of salt effect on the performances of corresponding DSSC, we find that increasing LiI concentration leads to increased short-circuit photocurrent density (Jsc) caused by enhanced I3− diffusion up to an LiI content of 28.9 wt %. Above this limitation, the Jsc decreases as a result of increased charge recombination caused by the further increased I3− concentration. The open-circuit voltage (Voc) increases gradually with LiI concentration owing to the enhanced I− content in DSSC. The optimized conversion efficiency is obtained at a salt content of 28.9 wt % in the “polymer-in-salt” region, with high ionic conductivity (1.06 × 10−3 S cm−1). Based on these facts, we suggest that the changes of conduction behavior and the changes of I3− and I− concentrations in the electrolytes contribute to the final performance variation of the corresponding DSSC with varying LiI concentration.
Co-reporter:Zuci Quan;Hao Hu;Sheng Xu;Wei Liu
Journal of Sol-Gel Science and Technology 2008 Volume 48( Issue 3) pp:261-266
Publication Date(Web):2008 December
DOI:10.1007/s10971-008-1825-x
Bi1−xCexFeO3 (x = 0, 0.05, 0.1, 0.15 and 0.20) (BCFO) thin films were deposited on Pt/TiN/Si3N4/Si substrates by sol–gel technique. Crystal structures, surface chemical compositions and bonding states of BCFO films were investigated by X-ray diffraction and X-ray photoelectron spectroscopy (XPS), respectively. Compared to BiFeO3 (BFO) counterparts, the fitted XPS narrow-scan spectra of Bi 4f7/2, Bi 4f5/2, Fe 2p3/2, Fe 2p1/2 and O 1s peaks for Bi0.8Ce0.2FeO3 film shift towards higher binding energy regions by amounts of 0.33, 0.29, 0.43, 0.58 and 0.49 eV, respectively. Dielectric constants and loss tangents of the BCFO (x = 0, 0.1 and 0.2) film capacitors are 159, 131, 116, 0.048, 0.041 and 0.035 at 1 MHz, respectively. Bi0.8Ce0.2FeO3 film has a higher remnant polarization (Pr = 2.04 μC/cm2) than that of the BFO (Pr = 1.08 μC/cm2) at 388 kV/cm. Leakage current density of the Bi0.8Ce0.2FeO3 capacitor is 1.47 × 10−4 A/cm2 at 388 kV/cm, which is about two orders of magnitude lower than that of the BFO counterpart. Furthermore, Ce cations are feasibly substituted for Bi3+ in the Bi0.8Ce0.2FeO3 matrix, possibly resulting in the enhanced ferroelectric properties for the decreased grain sizes and the reduced oxygen vacancies.
Co-reporter:Xiaohua Sun, Huiming Huang, Shengxiang Wang, Meiya Li, Xing-zhong Zhao
Thin Solid Films 2008 Volume 516(Issue 6) pp:1308-1312
Publication Date(Web):30 January 2008
DOI:10.1016/j.tsf.2007.06.155
A modified sol–gel method was used to fabricate (Pb0.25Bax Sr0.75−x)TiO3 (PBST) thin films with x = 0.05,0.1,0.15 and 0.2 on Pt/TiO2/SiO2/Si substrate. The structure, surface morphology, dielectric and tunable properties of PBST thin films were investigated as a function of barium content (x). X-ray diffraction and scanning electron microscopy analysis showed that we could get pure PBST perovskite phase and relative fine density thin films with smooth surface. It was found that the crystal lattice constant, grain size, room temperature dielectric constant, dielectric loss and tunability of Ba solutionizing PST thin films increased with the increase in Ba content. For (Pb0.25Ba0.2Sr0.55)TiO3 thin film, it had the highest dielectric constant of 1390 and the largest tunability of 80.6%. The figure of merit parameter reached a maximal value of 28.9 corresponding to the (Pb0.25Ba0.05 Sr0.7)TiO3 thin film, whose dielectric constant, dielectric loss and tunability measured at 1 MHz were 627, 0.024 and 69.4%, respectively.
Co-reporter:Jing Zhang, Hongwei Han, Sujuan Wu, Sheng Xu, Ying Yang, Conghua Zhou, Xingzhong Zhao
Solid State Ionics 2007 Volume 178(29–30) pp:1595-1601
Publication Date(Web):December 2007
DOI:10.1016/j.ssi.2007.10.009
Conductive carbon nanoparticles were introduced into PEO/P(VDF-HFP)/SiO2 nanocomposite polymer electrolyte for dye sensitized solar cells (DSSCs). The conductive mechanism is changed by adding different amount carbon nanoparticles: 2.5, 5, 7.5, and 15 wt.%. AC impedance measurements and DC voltage–current measurements were carried out to analyze the conductive mechanism of the composite polymer electrolyte (CPE in short). DSC thermograms also indicated the configuration change of the different carbon nanoparticles content modified CPE. Small amount of carbon nanoparticles modification improved the ionic conductivity and the solar to electric energy conversion efficiency of DSSC with 5 wt.% carbon nanoparticles modified CPE is improved to 4.27% compared with the original DSSC performance of 3.87%. Too much carbon nanoparticles content in CPE is unfavorable for the ionic conductivity and the electronic conductive path is formed in it. The efficiency of 15 wt.% carbon nanoparticles modified CPE type DSSC is decreased to 3.61%.
Co-reporter:Sujuan Wu, Qing Xu, Xingzhong Zhao, Tao Liu, Yueming Li
Materials Letters 2006 Volume 60(Issue 12) pp:1453-1458
Publication Date(Web):June 2006
DOI:10.1016/j.matlet.2005.11.044
The (Na0.5Bi0.5)0.94Ba0.06TiO3–0.6 wt.%CeO2 (abbreviated as NBT-BT6–0.6%CeO2) ceramic was synthesized by a citrate method. The effects of poling condition on piezoelectric properties of NBT-BT6-0.6%CeO2 ceramic and the influences of sintering temperature on its ferroelectric and piezoelectric properties were investigated. It was found that the piezoelectric properties of NBT-BT6–0.6%CeO2 ceramic highly rely upon poling field and poling temperature, while no remarkable effect of poling time on the piezoelectric properties was found in the range of 5–25 min. Moderate increase of sintering temperature improves the piezoelectric and ferroelectric properties of NBT-BT6–0.6%CeO2 ceramic. With respect to the piezoelectric and ferroelectric properties, a sintering temperature range of 1130–1170 °C is ascertained for NBT-BT6–0.6%CeO2 ceramic.
Co-reporter:Tianshu Wu, Binzhong Dong, Mingsen Guo, Xin Chen, Shishang Guo, Meiya Li, Xing-Zhong Zhao
Thin Solid Films 2006 Volume 497(1–2) pp:329-332
Publication Date(Web):21 February 2006
DOI:10.1016/j.tsf.2005.10.002
Growth and structural evolution of La0.5Sr0.5CoO3 thin films fabricated directly on SiO2/Si substrate by pulsed laser deposition were investigated. Films deposited at 780 °C and oxygen partial pressure of 2 Pa showed highly c-axis orientation. Films with low electrical resistivity of 2 × 10− 3 Ω cm were obtained by annealing at 650 °C for 40 min. C-axis oriented Ba0.5Sr0.5TiO3 thin film was then grown on the La0.5Sr0.5CoO3 film, and large dielectric tuning (> 50%) was achieved. This method may have good prospect for the integration of ferroelectric materials with conventional Si process technology.
Co-reporter:H. W. Han;W. Liu;J. Zhang;X.-Z. Zhao
Advanced Functional Materials 2005 Volume 15(Issue 12) pp:
Publication Date(Web):19 OCT 2005
DOI:10.1002/adfm.200500159
High-efficiency all-solid-state dye-sensitized nanocrystalline solar cells have been fabricated using a poly(ethylene oxide)/poly(vinylidene fluoride) (PEO/PVDF)/TiO2-nanoparticle polymer redox electrolyte, which yields an overall energy-conversion efficiency of about 4.8 % under irradiation by white light (65.2 mW cm–2). The introduction of PVDF (which contains the highly electronegative element fluorine) and TiO2 nanoparticles into the PEO electrolyte increases the ionic conductivity (by about two orders of magnitude) and effectively reduces the recombination rate at the interface of the TiO2 and the solid-state electrolyte, thus enhancing the performance of the solar cell.
Co-reporter:S.S. Guo, X.H. Sun, S.X. Wang, S. Xu, X.-Z. Zhao, Helen L.W. Chan
Materials Chemistry and Physics 2005 Volume 91(2–3) pp:348-354
Publication Date(Web):15 June 2005
DOI:10.1016/j.matchemphys.2004.11.038
Thermal and structural properties of high-energy electron irradiated ferroelectric blends by poly(vinylidene fluoride-trifluoroethylene) 56/44 and 80/20 mol% copolymers have been investigated by thermally stimulated depolarization current (TSDC), differential scanning calorimetry (DSC) and X-ray diffraction measurements. The temperature peaks observed in TSDC spectra of the blends decrease with the irradiation dose, associating phase transitional characters of the parent copolymers. And their distribution shows the existence of two types of crystallite, which become more clear after irradiation, demonstrating that the miscibility in the crystalline region for their large compositional discrepancy (24 mol% in their VF2 contents) in the blend. In DSC thermograms, it is found that the Curie temperature and melting temperature decrease with the dose. The ferroelectric-to-paraelectric (F–P) transition temperatures and enthalpies in the blends merge into one with the increasing of dose, which indicates a strong lattice coupling. X-ray diffraction shows some degree of mixing inside a crystal lattice due to significant changes in the F–P phase transition behavior from all-trans to trans-gauche conformation in nanometer range after irradiation.
Co-reporter:Cheng-Liang Sun, S.S. Guo, W.P. Li, Z.B. Xing, G.C. Liu, X.-Z. Zhao
Sensors and Actuators A: Physical 2005 Volume 121(Issue 1) pp:213-220
Publication Date(Web):31 May 2005
DOI:10.1016/j.sna.2005.01.023
The cymbal transducer consists of an inner P-5 piezoelectric disk mechanically coupled to two thin brass end caps on each of its electrode faces by eccobond epoxy. The caps serve as mechanical transformers for converting and amplifying the small radial displacement and vibration velocity of the ceramic disk into a much larger axial displacement and vibration velocity normal to the surface of the caps. Based on previous studies of cymbal transducers, the displacement amplification and the properties of resonance of the cymbal were elevated by optimizing the fabrication technique. Several kinds of end caps were designed and some theoretical models were used for the cymbals to study their performances based on the cavity depth and caps thickness. They showed more than 14× to 38× amplification over the uncapped ceramic alone under the direct current (dc) mode. And under the alternating current (ac) mode, the cymbals showed much larger peak-to-peak displacement than dc displacement. Effective piezoelectric charge coefficient of the cymbal reached to 22,550 pm/V. The cymbals also showed the first resonance frequency from 28.54 to 58.53 kHz and faster resonance time about several tens of microseconds.
Co-reporter:S. S. Guo;S. G. Lu;Z. K. Xu;X.-Z. Zhao
Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 21) pp:2972-2980
Publication Date(Web):13 SEP 2005
DOI:10.1002/polb.20584
The relaxor ferroelectric (RFE) behavior in high-energy electron-irradiated poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] 80/20 mol % copolymer system is characterized over a broad frequency and temperature range. The dielectric properties remarkably vary with the irradiated dose in terms of the change from normal ferroelectric (FE) to RFE phase. During the RFE–paraelectric (PE) transition, the dielectric constants, as a function of temperature, can be described by the Vogel–Fulcher (V–F) relation. It has been found that the relationship between the real and imaginary part of dielectric constant in irradiated copolymer can be well fitted with modified Cole–Cole equation and Debye relaxation equation, exhibiting similar features as inorganic RFEs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2972–2980, 2005
Co-reporter:Weiping Li;Yiwen Tang;Xingzhong Zhao;Shishang Guo
Journal of Applied Polymer Science 2004 Volume 91(Issue 5) pp:2903-2907
Publication Date(Web):14 JAN 2004
DOI:10.1002/app.13503
The electron irradiation effect on 80/20 poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] copolymers was studied by FTIR spectra and X-ray diffraction. Infrared spectra showed decreasing intensity of bands at 1430, 1286, 846, and 505 cm−1, the appearance and intensity increasing with irradiation doses of bands at 768, 601, and 1735 cm−1, which revealed the conformational change after irradiation. The X-ray diffraction patterns exhibited a decrease of volume fraction of ferroelectric phase and expansion of the lattice space. The electron-irradiated P(VDF–TrFE) films showed structural changes and polar phase to nonpolar phase transformation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2903–2907, 2004
Co-reporter:Hongwei Han, Ling Zan, Jiasheng Zhong, Lina Zhang, Xingzhong Zhao
Materials Science and Engineering: B 2004 Volume 110(Issue 2) pp:227-232
Publication Date(Web):15 July 2004
DOI:10.1016/j.mseb.2004.03.019
A high-surface-area nanocrystalline TiO2 films were successfully prepared from two kinds of easy-reaggregation primary nanoparticles with the mean size of 26 nm in ethanol solution by a novel technique of quickly volatilizing solvent to fix the nanoparticles. Structure and properties of the films were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that the mean size of nanoparticles does not change with heat-treatment at 450 °C and the roughness factor about 86 and 80 was obtained for 1 μm thickness films. A roughness factor of 82 was found for the commercial P25 TiO2 films with the mean size of 36 nm and the same thickness. The electrochemical properties of the bare interfaces of the TiO2 film electrodes in propylene carbonate (PC) containing 0.05 M tetrabutyl ammonium bromide (TBAB) was also measured and show that the electroactive of the TiO2(I) film is similar to P25. Moreover, this method is adapted to prepare nanostructural films using other materials and smaller primary nanoparticles for dye-sensitized nanocrystalline solar cells.
Co-reporter:Long Cheng, Bo Cai, Yunfeng Zuo, Liang Xiao, Lang Rao, Zhaobo He, Yi Yang, Wei Liu, Shishang Guo, Xing-Zhong Zhao
Chemical Physics Letters (April 2017) Volume 673() pp:
Publication Date(Web):April 2017
DOI:10.1016/j.cplett.2017.02.030
•Realizing Janus droplet parallel arrangements by simply modulating fluid flow rates in microchannels.•Analyzing the formation of droplet arrangements as well as their transition thresholds.•Visualizing the material convection between hemispheres of the Janus droplets and their rolling.Due to its unique advantages such as monodispersity and high throughput, droplet microfluidics has been widely used to generate diverse droplets/particles that have specific structures. Herein, we implemented Janus droplet parallel arrangements in a flow-focusing microchip through regulating corresponding fluid flow rates. Initially, fluorescence dye and PBS buffer solution kept laminar flow before the flow-focusing orifice and then was sheared into Janus droplets. Droplet diameter and corresponding generation frequency could be effectively manipulated. Subsequently, the generation of different Janus droplet parallel arrangements (e.g. monolayer, double-layer or three-layer arrangement) could be achieved by fluid regulation.
Co-reporter:Liang Xiao, Zhao-Bo He, Bo Cai, Lang Rao, Long Cheng, Wei Liu, Shi-Shang Guo, Xing-Zhong Zhao
Chemical Physics Letters (16 January 2017) Volume 668() pp:
Publication Date(Web):16 January 2017
DOI:10.1016/j.cplett.2016.12.014
•We synthesized core-shell Fe3O4@MnO2 nanoparticles.•We captured target-cells with good efficiency.•The captured cells could be released.•The released cells kept good viability.Circulating tumor cells (CTCs) have been believed to hold significant insights for cancer diagnosis and therapy. Here, we developed a simple and effective method to capture and release viable CTCs using core-shell Fe3O4@MnO2 nanoparticles. Fe3O4@MnO2 nanoparticles bioconjugated with anti-EpCAM antibody have characteristics of specific recognition, magnetic-driven cell isolation and oxalic acid-assisted cell release. The capture and release efficiency of target cancer cells were ∼83% and ∼55%, respectively. And ∼70% of released cells kept good viability, which could facilitate the subsequent cellular analysis.
Co-reporter:Xing-Hu Ji, Nan-Gang Zhang, Wei Cheng, Feng Guo, Wei Liu, Shi-Shang Guo, Zhi-Ke He and Xing-Zhong Zhao
Journal of Materials Chemistry A 2011 - vol. 21(Issue 35) pp:NaN13387-13387
Publication Date(Web):2011/08/03
DOI:10.1039/C1JM12253C
In this paper we describe a versatile microfluidic strategy for simultaneous preparation of quantum dot-encoded microbeads with controllable barcodes. This method involves the generation of multiple dispersed solutions carrying stepwise concentration gradients of quantum dots by using a pyramidal microfluidic network, the formation of corresponding droplets in parallel flow-focusing droplet generators, and on-chip solidification of these droplets into microbeads. Using a designed microfluidic device, we simultaneously generated five kinds of fluorescence-encoded alginate hydrogel microbeads with a five-level stepwise concentration gradient of monochromatic quantum dot or five controllable ratios of two different-sized quantum dots. This method has the following features: (1) the barcode adapter compartment substitutes the respective preparation of precursor solutions containing the correct concentrations and ratios of different quantum dots for corresponding barcodes. (2) Identical microbeads with distinct quantum dot barcodes can be simultaneously generated in homogeneous conditions. (3) The microfluidic device can be upgraded by increasing or decreasing the inlets and outlets of the pyramidal network and the number of the parallel flow-focusing droplet generators to meet the requirements for the particular barcodes. We expect that this microfluidic route will facilitate the construction and mass-production of robust and reproducible barcode materials.
Co-reporter:Weiwei Sun, Tao Peng, Yumin Liu, Sheng Xu, Jikang Yuan, Shishang Guo and Xing-Zhong Zhao
Journal of Materials Chemistry A 2013 - vol. 1(Issue 8) pp:NaN2768-2768
Publication Date(Web):2013/01/07
DOI:10.1039/C2TA01000C
Hierarchically porous polyaniline–reduced graphene oxide hybrids have been developed via oxidative polymerization of aniline by MnO2 on reduced graphene sheets under acidic conditions (named M-PANI@rGO). The formation mechanism of the above hybrids indicates that the MnO2 undergoes oxidative disintegration and results in the porous structure of polyaniline (PANI) nanoparticle formation on the reduced graphene oxide (rGO) surface. The scanning electron microscopy (SEM) images and Brunauer–Emmett–Teller (BET) nitrogen sorption–desorption measurement clearly showed the nanoporous nature of the M-PANI@rGO hybrids. TEM-EDX confirmed the complete removal/degradation of MnO2 during the oxidative polymerization of aniline. Just for comparison, PANI–rGO hybrids have also been prepared via conventional polymerization using (NH4)2S2O8 as the oxidant (named C-PANI@rGO). When these different architectural PANI@rGO hybrids were applied as the counter electrode for dye-sensitized solar cells (DSSCs), the short-circuit current density (Jsc) and power-conversion efficiency (η) of the DSSCs with C-PANI@rGO hybrids are measured to be 11.64 mA cm−2 and 5.62%, respectively, while the corresponding values are 12.88 mA cm−2 and 6.15% for the DSSCs with M-PANI@rGO hybrids, which is comparable to 6.73% for the cell with a Pt counter electrode under the same experimental conditions. The hierarchically porous M-PANI@rGO hybrid is thus a promising candidate to replace platinum as a counter electrode for DSSCs.
Co-reporter:Qidong Tai and Xing-Zhong Zhao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 33) pp:NaN13218-13218
Publication Date(Web):2014/06/16
DOI:10.1039/C4TA01404A
Bifacial dye-sensitized solar cells (DSCs) that are able to utilize the incidental light from both their front- and rear-side have received increasing attention in recent years. Compared to conventional DSCs that can only be operated under front-side illumination, bifacial design will allow DSCs to generate up to 50% more electrical power. Besides, bifacial DSCs can be easily made transparent and may find broad applications in building integrated photovoltaics (BIPV) as power-generating windows and roof panels. Transparent counter electrodes (CEs) are key to the fabrication of bifacial DSCs. However, despite the fact that conventional Pt CE can be made transparent, its high cost and scarce source may hinder the large-scale application of DSCs. Therefore, many efforts have been made to develop low-cost alternative CEs based on carbon materials, conducting polymers, inorganic compounds and their composites. In this feature article, we intend to pay special attention to the recent advances in the development of Pt-free transparent CEs and highlight their applications in bifacial DSCs.
Co-reporter:Pingli Qin, Guojia Fang, Weijun Ke, Fei Cheng, Qiao Zheng, Jiawei Wan, Hongwei Lei and Xingzhong Zhao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 8) pp:NaN2756-2756
Publication Date(Web):2013/11/25
DOI:10.1039/C3TA13579A
Efficient organic solar cells (OSCs) based on regioregular poly(3-hexylthiophene):fullerene derivative [6,6]-phenyl-C61butyric acid methyl ester composites have been fabricated on fluorine-doped tin oxide (FTO) coated glass substrates by a radio frequency (RF) sputtered and ultraviolet ozone (UVO) treated MoS2 film as the hole-transport layer (HTL). With the help of X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, Raman spectroscopy, transmission spectra and the Hall-effect system, we find that the deposition temperature can modulate the contents of the various valence states of molybdenum, which can result in changes of the energy level, and the optical and electrical properties of the MoS2 films. MoS2 has been oxidized to a double-layered MoO3–MoS2 film by UVO treatment. Due to the presence of the molybdenum oxidation states Mo5+ and Mo6+, the MoS2 film shows p-type conductive behavior, and its smaller electron affinity can effectively block electron from exciton dissociation. By optimizing the HTL thickness and sputtering deposition temperature, a power conversion efficiency up to 4.15% has been achieved for an OSC that used a double-layered MoO3–MoS2 film as the HTL. Its JSC is bigger than that of the OSC with a pure MoO3 film as the HTL. This shows that this double layer MoO3–MoS2 interface is more favorable for hole-transfer.
Co-reporter:Changlei Wang, Dewei Zhao, Corey R. Grice, Weiqiang Liao, Yue Yu, Alexander Cimaroli, Niraj Shrestha, Paul J. Roland, Jing Chen, Zhenhua Yu, Pei Liu, Nian Cheng, Randy J. Ellingson, Xingzhong Zhao and Yanfa Yan
Journal of Materials Chemistry A 2016 - vol. 4(Issue 31) pp:NaN12087-12087
Publication Date(Web):2016/07/11
DOI:10.1039/C6TA04503K
Recent progress has shown that low-temperature processed tin oxide (SnO2) is an excellent electron selective layer (ESL) material for fabricating highly efficient organic–inorganic metal-halide perovskite solar cells with a planar cell structure. Low-temperature processing and a planar cell structure are desirable characteristics for large-scale device manufacturing due to their associated low costs and processing simplicity. Here, we report that plasma-enhanced atomic layer deposition (PEALD) is able to lower the deposition temperature of SnO2 ESLs to below 100 °C and still achieve high device performance. With C60-self-assembled monolayer passivation, our PEALD SnO2 ESLs deposited at ∼100 °C led to average power conversion efficiencies higher than 18% (maximum of 19.03%) and 15% (maximum of 16.80%) under reverse voltage scan for solar cells fabricated on glass and flexible polymer substrates, respectively. Our results thus demonstrate the potential of the low-temperature PEALD process of SnO2 ESLs for large-scale manufacturing of efficient perovskite solar cells.
Co-reporter:Weiwei Sun, Huiqin Liu, Tao Peng, Yumin Liu, Gongxun Bai, Sen Kong, Shishang Guo, Meiya Li and Xing-Zhong Zhao
Journal of Materials Chemistry A 2015 - vol. 3(Issue 15) pp:NaN8170-8170
Publication Date(Web):2015/03/06
DOI:10.1039/C5TA00752F
Porous micrometer-sized architecture that consists of aggregated single-crystalline nanoparticles is critical for LiMn2O4 to achieve good rate capacity and cycling stability, since it can increase the contact area between the electrolyte/electrode and shorten the transport paths for electrons and lithium ions. In this paper, hierarchical porous donut-shaped LiMn2O4 comprising aggregated single-crystalline nanoparticles has been successfully fabricated with MnO2 nanosheet coated polystyrene spheres as a precursor and characterized in terms of structure and performance as the cathode for lithium ion batteries. The charge/discharge tests show that the as-obtained donut-shaped LiMn2O4 exhibits excellent rate capability and high-rate cyclic stability. Surprisingly, even at a high charge/discharge rate of 10 C, the battery yields a capacity retention of over 95% after 500 cycles. The superior performance of the synthesized product can be attributed to its intrinsic structure: porous donut-shaped LiMn2O4 consisting of well-connected single-crystalline nanoparticles. The interpenetrating nanoparticle reduces the path of Li ion diffusion and increases the number of reaction sites for lithium insertion/extraction; the pores provide void space to buffer the volume changes during high-rate charge/discharge.
Co-reporter:Zhaobo He, Feng Guo, Chun Feng, Bo Cai, James P. Lata, Rongxiang He, Qinqin Huang, Xiaolei Yu, Lang Rao, Huiqin Liu, Shishang Guo, Wei Liu, Yuanzhen Zhang, Tony Jun Huang and Xingzhong Zhao
Journal of Materials Chemistry A 2017 - vol. 5(Issue 2) pp:NaN235-235
Publication Date(Web):2016/11/23
DOI:10.1039/C6TB02558G
Cell-free DNA has been widely used in non-invasive prenatal diagnostics (NIPD) nowadays. Compared to these incomplete and multi-source DNA fragments, fetal nucleated red blood cells (fNRBCs), once as an aided biomarker to monitor potential fetal pathological conditions, have re-attracted research interest in NIPD because of their definite fetal source and the total genetic information contained in the nuclei. Isolating these fetal cells from maternal peripheral blood and subsequent cell-based bio-analysis make maximal genetic diagnosis possible, while causing minimal harm to the fetus or its mother. In this paper, an affinity microchip is reported which uses hydroxyapatite/chitosan nanoparticles as well as immuno-agent anti-CD147 to effectively isolate fNRBCs from maternal peripheral blood, and on-chip biomedical analysis was demonstrated as a proof of concept for NIPD based on fNRBCs. Tens of fNRBCs can be isolated from 1 mL of peripheral blood (almost 25 mL−1 in average) from normal pregnant women (from the 10th to 30th gestational week). The diagnostic application of fNRBCs for fetal chromosome disorders (Trisomy 13 and 21) was also demonstrated. Our method offers effective isolation and accurate analysis of fNRBCs to implement comprehensive NIPD and to enhance insights into fetal cell development.
Co-reporter:Jun-Hua Xu, Fu-Ping Gao, Xue-Feng Liu, Qian Zeng, Shi-Shang Guo, Zhi-Yong Tang, Xing-Zhong Zhao and Hao Wang
Chemical Communications 2013 - vol. 49(Issue 40) pp:NaN4464-4464
Publication Date(Web):2013/03/07
DOI:10.1039/C3CC00304C
We demonstrate the on-chip preparation of size-controllable supramolecular gelatin nanoparticles (SGNs) with a quantum dot (QD) payload as matrix metalloproteinase (MMP) responsive cancer cell imaging probes.
Co-reporter:Liangliang Liang, Yumin Liu and Xing-Zhong Zhao
Chemical Communications 2013 - vol. 49(Issue 38) pp:NaN3960-3960
Publication Date(Web):2013/03/25
DOI:10.1039/C3CC41252K
Double-shell β-NaYF4:Yb3+, Er3+/SiO2/TiO2 submicroplates have been used as a scattering and upconverting layer for dye-sensitized solar cells (DSSCs). Due to their effective light scattering and upconverting effects, the performance of DSSCs was significantly enhanced, resulting in an efficiency of 7.70%, which is a noticeable improvement of ∼29.41% compared to the cell without the bifunctional layer (5.95%).
Co-reporter:Zhenhua Yu, Sujian You, Changlei Wang, Chenghao Bu, Sihang Bai, Ziyao Zhou, Qidong Tai, Wei Liu, Shishang Guo and Xing-zhong Zhao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 24) pp:NaN9010-9010
Publication Date(Web):2014/03/18
DOI:10.1039/C4TA00837E
A highly environmentally-friendly ubiquinone 10 (UQ10) based I2-free electrolyte, which is inspired by photosynthesis, is employed in dye-sensitized solar cells (DSSCs) under 100 mW cm−2 (AM 1.5G) illumination. Profiting from this UQ10 based electrolyte a 10% increased power conversion efficiency of 8.18% is achieved compared with the traditional one containing I2 (7.44%). The superior performance of this UQ10 based electrolyte is mainly derived from the lower visible light wastage and high catalytic activity to the counter electrode as revealed by photoelectrochemical characterization. Moreover, being widely adopted in cardiovascular medicine and cosmetics, UQ10 is a very safe and low-cost choice for DSSCs. With the advantages of high power conversion efficiency, bio-safety, universal dye compatibility and diversity of molecular design, UQ10 is very promising to be widely applied in DSSCs, and perovskite based solar cells.
